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Saad Tayyab - One of the best experts on this subject based on the ideXlab platform.
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behavior of various mammalian albumins towards Bilirubin Binding and photochemical properties of different Bilirubin albumin complexes
International Journal of Biological Macromolecules, 2003Co-Authors: Saad Tayyab, Mateen A Khan, Nida J Khan, Yogesh KumarAbstract:Bilirubin (BR) Binding properties of serum albumins from different mammalian species viz. human (HSA), equine (ESA), dog (DSA) and guinea pig (GPSA) were studied by absorption, fluorescence and CD spectroscopy. Whereas, a complex of BR with ESA produced maximum change, GPSA-BR complex showed weaker interaction as reflected from absorption and fluorescence spectroscopic data. Conformational analysis of these albumins by near- and far-UV CD spectra suggested similar structural characteristics (both secondary and tertiary structures) for ESA and HSA, whereas, DSA and GPSA had lower amounts of secondary and tertiary structures being minimum for GPSA. Photoirradiation results of BR-albumin complexes showed GPSA-bound BR more labile compared with other complexes, whereas, BR-ESA complex was found to be more stable against photoinduced chemical changes. Taken together, all these results suggest that chiroptical properties/stability of albumin bound BR varies with albumin species.
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Bilirubin Binding properties of pigeon serum albumin and its comparison with human serum albumin
International Journal of Biological Macromolecules, 2002Co-Authors: Mateen A Khan, Yogesh Kumar, Saad TayyabAbstract:Binding of Bilirubin (BR) to pigeon serum albumin (PgSA) was studied by absorption, fluorescence and CD spectroscopy and results were compared with those obtained with human serum albumin (HSA). PgSA was found to be structurally similar to HSA as judged by near- and far-UV CD spectra. However, PgSA lacks tryptophan. Binding of BR to PgSA showed relatively weaker interaction compared to HSA in terms of Binding affinity, induced red shift in the absorption spectrum of BR and CD spectral characteristics of BR-albumin complexes. Photoirradiation results of BR-albumin complexes also showed PgSA-bound BR more labile compared to HSA-bound BR.
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understanding the role of internal lysine residues of serum albumins in conformational stability and Bilirubin Binding
Biochimica et Biophysica Acta, 2001Co-Authors: Mohd Mushahid Khan, Saad TayyabAbstract:The role of internal lysine residues of different serum albumins, viz. from human, rabbit, goat, sheep and buffalo (HSA, RbSA, GSA, SSA and BuSA), in conformational stability and Bilirubin Binding was investigated after blocking them using acetylation, succinylation and guanidination reactions. No significant change in the secondary structure was noticed whereas the tertiary structure of these proteins was slightly altered upon acetylation or succinylation as revealed by circular dichroism (CD), fluorescence and gel filtration results. Guanidination did not affect the native protein conformation to a measurable extent. Scatchard analysis, CD and absorption spectroscopic results showed marked reductions (5-21-fold decrease in K(a) and approximately 50% decrease in the CD Cotton effect intensity) in the affinity of albumins for Bilirubin upon acetylation or succinylation whereas guanidination produced a small change. Interestingly, monosignate CD spectra of Bilirubin complexed with GSA, SSA and BuSA were transformed to bisignate CD spectra upon acetylation or succinylation of internal lysine residues whereas spectra remained bisignate in the case of Bilirubin bound to acetylated or succinylated derivatives of HSA and RbSA. When probed by CD spectroscopy, Bilirubin bound to acetylated or succinylated derivatives of GSA and SSA rapidly switched over to native albumins and not vice versa. These results suggested that salt linkage(s) contributed by internal lysine residue(s) play an important role in the high-affinity Binding of Bilirubin to albumin and provide stability to the native three-dimensional conformation of the bound pigment. Chloroform severely decreased the intensity of both positive and negative CD Cotton effects of Bilirubin complexed with acetylated or succinylated derivatives of all albumins which otherwise increased significantly in the case of Bilirubin complexed with native and guanidinated albumin derivatives, except the Bilirubin-RbSA complex which showed a small decrease in intensity. These results suggest that the presence of salt linkage(s) in Bilirubin-albumin complexation is(are) crucial to bring about effective and efficient stereochemical changes in the bound pigment by co-Binding of chloroform which seems to have at least one conserved Binding site on these albumins that is shared with Bilirubin.
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role of salt bridge s in the Binding and photoconversion of Bilirubin bound to high affinity site on human serum albumin
Biochimica et Biophysica Acta, 2000Co-Authors: Mohd Mushahid Khan, Salman Muzammil, Saad TayyabAbstract:The role of salt bridge(s) (between ϵ-NH2 groups of lysine residues of human serum albumin (HSA) and carboxyl groups of Bilirubin) in the Binding and photoconversion of Bilirubin bound to high affinity site on HSA was investigated by covalent modification of ∼20% internal (buried) lysine residues of HSA with acetic anhydride, succinic anhydride and O-methylisourea and white light irradiation of their complexes with Bilirubin. The different HSA derivatives, namely, acetylated HSA (aHSA), succinylated HSA (sHSA) and guanidinated HSA (gHSA), thus obtained, were found to be homogeneous with respect to charge and size and characterized in detail in terms of mean residue ellipticity, Stokes radius, tryptophan fluorescence, Bilirubin Binding and the photochemistry of their complexes with Bilirubin. All the three derivatives retained helical contents and molecular size (Stokes radius) similar to HSA except for sHSA which showed a slight increase in the Stokes radius from 3.56 to 3.64 nm. Further, fluorescence properties of aHSA and sHSA were also found to be different from HSA and gHSA. Based on difference spectral change, fluorescence quenching and fluorescence enhancement results of Bilirubin bound to HSA and its derivatives, nearly 46 and 48% reduction in Bilirubin Binding was observed in the case of aHSA and sHSA, respectively. Both aHSA and sHSA showed a decrease of 8- and 10-fold, respectively, in association constant compared to native HSA. Although the bisignate circular dichroism (CD) spectra of an equimolar (1:1) Bilirubin–HSA complex was retained by all three HSA derivatives, the intensity of both positive and negative CD Cotton effects decreased significantly in both aHSA and sHSA. gHSA which retained net charge identical to native HSA, showed little decrease in Bilirubin Binding and the intensity of bisignate CD Cotton effects. The photochemical reaction of Bilirubin bound to aHSA and sHSA produced opposite results to those observed with HSA and gHSA. A brief (2 min) irradiation of an equimolar complex of Bilirubin with both aHSA and sHSA accompanied a rapid shift (14–15 nm) in the absorption spectrum of the bound pigment towards the blue region and almost complete elimination of negative CD Cotton effects while only moderately affecting the magnitude of positive CD Cotton effects. On the other hand, similar treatment of the complexes of Bilirubin with HSA and gHSA did not show any change in the absorption spectrum, only a slight decrease in the intensity of both positive and negative CD Cotton effects was observed. The fluorescence intensity of Bilirubin bound to HSA and gHSA was increased upon irradiation with white light and after 30 min it was nearly twice the value observed at 0 min irradiation. Interestingly, no change in the fluorescence intensity of Bilirubin bound either to aHSA or sHSA was observed upon irradiation, even on increasing the duration of irradiation to 1 h. Taken together, the results on fluorescence quenching, fluorescence enhancement, CD spectral changes and visible absorption spectroscopy suggest that salt bridge(s) of the type (–COO−....+H3N–) in which the ϵ-NH2 group(s) contributed by lysine residues, are not only involved in the enantioselective Binding of Bilirubin but also in the stereospecific photoisomerization of Bilirubin bound to a high affinity site on HSA.
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effect of ph and temperature on the Binding of Bilirubin to human erythrocyte membranes
Journal of Biosciences, 2000Co-Authors: Huma Rashid, Mohammad Ali, Saad TayyabAbstract:Effect of pH and temperature on the Binding of Bilirubin to human erythrocyte membranes was studied by incubating the membranes at different pH and temperatures and determining the bound Bilirubin. At all pH values, the amount of membrane-bound Bilirubin increased with the increase in Bilirubin-to-albumin molar ratios (B/As), being highest at lower pH values in all cases. Further, linear increase in bound Bilirubin with the increase in Bilirubin concentration in the incubate was observed at a constant B/A and at all pH values. However, the slope value increased with the decrease in pH suggesting more Bilirubin Binding to membranes at lower pH values. Increase in Bilirubin Binding at lower pH can be explained on the basis of increased free Bilirubin concentration as well as more conversion of Bilirubin dianion to monoanion. Temperature dependence of Bilirubin Binding to membranes was observed within the temperature range of 7°–60°C, showing minimum Binding at 27°C and 37°C which increased on either side. Increase in Bilirubin Binding at temperatures lower than 20°C and higher than 40°C can be ascribed to the change in membrane topography as well as Bilirubin-albumin interaction.
Sanjiv B. Amin - One of the best experts on this subject based on the ideXlab platform.
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Bilirubin Binding capacity in the preterm neonate
Clinics in Perinatology, 2016Co-Authors: Sanjiv B. AminAbstract:Total serum/plasma Bilirubin (TB), the biochemical measure currently used to evaluate and manage hyperBilirubinemia, is not a useful predictor of Bilirubin-induced neurotoxicity in premature infants. Altered Bilirubin-albumin Binding in premature infants limits the usefulness of TB in premature infants. In this article, Bilirubin-albumin Binding, a modifying factor for Bilirubin-induced neurotoxicity, in premature infants is reviewed.
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Newborn Jaundice Technologies: Unbound Bilirubin and Bilirubin Binding Capacity in Neonates
Seminars in perinatology, 2011Co-Authors: Sanjiv B. Amin, Angelo A. LamolaAbstract:Neonatal jaundice (hyperBilirubinemia), which is extremely common in neonates, can be associated with neurotoxicity. A safe level of Bilirubin has not been defined in either premature or term infants. Emerging evidence suggest that the level of unbound (or "free") Bilirubin has a better sensitivity and specificity than total serum Bilirubin for Bilirubin-induced neurotoxicity. Although recent studies suggest the usefulness of free Bilirubin measurements in managing high-risk neonates, including premature infants, no widely available method exists to assay the serum free Bilirubin concentration. To keep pace with the growing demand, in addition to reevaluation of old methods, several promising new methods are being developed for sensitive, accurate, and rapid measurement of free Bilirubin and Bilirubin Binding capacity. These innovative methods need to be validated before adopting for clinical use. We provide an overview of some promising methods for free Bilirubin and Binding capacity measurements with the goal to enhance research in this area of active interest and apparent need.
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effect of free fatty acids on Bilirubin albumin Binding affinity and unbound Bilirubin in premature infants
Journal of Parenteral and Enteral Nutrition, 2010Co-Authors: Sanjiv B. AminAbstract:Background: The author has previously shown that intravenous lipid intake may be associated with an increase in unbound Bilirubin in infants ≤28 weeks gestational age. The objective of this study was to evaluate whether this increase in unbound Bilirubin is mediated by free fatty acids and to examine the secondary effect of free fatty acids on Bilirubin–albumin Binding affinity. Methods: A prospective study was conducted to include 26 infants ≤32 weeks gestational age with indirect hyperBilirubinemia and receiving intravenous lipids during the first 10 postnatal days. Blood samples were collected for unbound Bilirubin, Binding affinity, and free fatty acid measurement at varying intravenous lipid intakes (1–3 g/kg/d). Regression analyses were performed to evaluate the roles of free fatty acids and Binding affinity as mediators. Results: Intravenous lipid intake was significantly associated with an increase in free fatty acids and unbound Bilirubin in infants ≤28 weeks but not >28 weeks gestational age. In...
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intravenous lipid and Bilirubin albumin Binding variables in premature infants
Pediatrics, 2009Co-Authors: Sanjiv B. Amin, Theresa Harte, Lori Scholer, Hongyue WangAbstract:Intravenous lipid emulsion (IL) provides a concentrated isotonic source of calories in neonates. Clearance of free fatty acids (FFAs) is slower in premature infants than in term infants, and IL intake in premature infants may result in elevated FFA.1–3 The elevated FFA concentration may displace Bilirubin from albumin-Binding sites, increasing free or unbound Bilirubin (Bf, Bilirubin not bound to albumin) concentration.1,4–6 Bf crosses the intact blood-brain barrier and may cause brain injury, according to the current theory on the pathogenesis of Bilirubin-induced neurotoxicity.7–9 There is limited knowledge on the effect of increasing IL intake in premature infants on Bf concentrations.10–12 Current literature suggests that the Bilirubin-displacing effect may be seen at FFA to albumin molar (F/A) ratios of >4:1.10 Previous studies have shown that an F/A ratio of >4:1 may occur with IL intake of 2 to 3 g/kg per day in infants of ≤30 weeks’ gestational age (GA).10 Because of the potential for the Bilirubin-displacing effect at higher IL doses, IL intake is usually limited to <2 g/kg per day in the presence of indirect hyperBilirubinemia in premature infants, irrespective of the degree of prematurity.13,14 However, the evidence to support the practice of restricting the amount of IL intake during hyperBilirubinemia has been based on indirect estimation of Bf using fluorometer or saturation index tests in a small number of premature infants.10,11 Recently, the Food and Drug Administration approved an unbound Bilirubin analyzer, a semiautomated spectrophotometer, for Bf measurement using the peroxidase method.15,16 The peroxidase method was subsequently modified using 2 concentrations of peroxidase to avoid underestimation of Bf.17 There is little information on the effect of a gradual increase in IL intake from 1.5 to 3 g/kg per day on Bilirubin-albumin Binding variables, as measured by the modified peroxidase test using an unbound Bilirubin analyzer.12 It is also unclear if the effect of IL intake on Bilirubin-albumin Binding variables, specifically Bilirubin Binding affinity and Bf concentration, varies as a function of GA.
Charles E. Ahlfors - One of the best experts on this subject based on the ideXlab platform.
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Bilirubin Binding in jaundiced newborns from bench to bedside
Pediatric Research, 2018Co-Authors: Charles E. Ahlfors, Ronald J Wong, Vinod K Bhutani, David K StevensonAbstract:Background: Bilirubin-induced neurologic dysfunction (BIND) is a spectrum of preventable neurological sequelae in jaundiced newborns. Current total plasma Bilirubin (BT) concentration thresholds for phototherapy and/or exchange transfusion poorly predict BIND. Methods: The unbound (free) Bilirubin (Bf) measured at these BT thresholds provides additional information about the risk for BIND. Bf can be readily adapted to clinical use by determining Bf population parameters at current BT thresholds. These parameters can be established using a plasma Bilirubin Binding panel (BBP) consisting of BT, Bf, and two empiric constants, the maximum BT (BTmax) and the corresponding equilibrium association Bilirubin constant (K). Results: BTmax and K provide the variables needed to accurately estimate Bf at BT < BTmax to obtain Bf at threshold BT in patient samples. Once Bf population parameters are known, the BBP in a newborn can be used to identify poor Bilirubin Binding (higher Bf at the threshold BT compared with the population) and increased risk of BIND. Conclusion: The BBP can also be used in jaundice screening to better identify the actual BT at which intervention would be prudent. The BBP is used with current BT thresholds to better identify the risk of BIND and whether and when to intervene.
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the Bilirubin Binding panel a henderson hasselbalch approach to neonatal hyperBilirubinemia
Pediatrics, 2016Co-Authors: Charles E. AhlforsAbstract:Poor plasma Bilirubin Binding increases the risk of Bilirubin neurotoxicity in newborns with hyperBilirubinemia. New laboratory tests may soon make it possible to obtain a complete Bilirubin Binding panel when evaluating these babies. The 3 measured components of the panel are the plasma total Bilirubin concentration (BTotal), which is currently used to guide clinical care; the Bilirubin Binding capacity (BBC); and the concentration of non-albumin bound or free Bilirubin (BFree). The fourth component is the Bilirubin-albumin equilibrium dissociation constant, KD, which is calculated from BTotal, BBC, and BFree The Bilirubin Binding panel is comparable to the panel of components used in the Henderson-Hasselbalch approach to acid-base assessment. Bilirubin Binding population parameters (not prospective studies to determine whether the new Bilirubin Binding panel components are better predictors of Bilirubin neurotoxicity than BTotal) are needed to expedite the clinical use of Bilirubin Binding. At any BTotal, the BFree and the relative risk of Bilirubin neurotoxicity increase as the KD/BBC ratio increases (ie, Bilirubin Binding worsens). Comparing the KD/BBC ratio of newborns with BTotal of concern with that typical for the population helps determine whether the risk of Bilirubin neurotoxicity varies significantly from the inherent risk at that BTotal Furthermore, the Bilirubin Binding panel individualizes care because it helps to determine how aggressive intervention should be at any BTotal, irrespective of whether it is above or below established BTotal guidelines. The Bilirubin Binding panel may reduce anxiety, costs, unnecessary treatment, and the likelihood of undetected Bilirubin neurotoxicity.
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Bilirubin Binding contributes to the increase in total Bilirubin concentration in newborns with jaundice.
Pediatrics, 2010Co-Authors: Charles E. Ahlfors, Anne E ParkerAbstract:OBJECTIVE: This study tests the hypothesis that the hourly rate of increase in plasma Bilirubin concentration (ΔBT) would increase significantly with increasing Binding avidity. METHODS: The plasma total Bilirubin concentration (BT), unbound Bilirubin concentration, and albumin concentration values for healthy newborns with jaundice (≤100 hours of age, ≥35 weeks of gestation, and ≥2.5 kg at birth) were obtained from medical records. ΔBT (in milligrams per deciliter per hour) was calculated as the slope of BT versus age (in hours). Binding avidity was quantified as the product of the albumin concentration and its Bilirubin Binding constant (K). Linear correlation was used to test the hypothesis that ΔBT would increase significantly with K·albumin concentration. RESULTS: The ranges of BT, unbound Bilirubin concentration, albumin concentration, and K values for the 21 patients studied were 7.6 to 28.5 mg/dL, 0.53 to 2.52 μg/dL, 2.9 to 4.6 g/dL, and 38 to 163 L/μmol, respectively. ΔBT correlated significantly with K·albumin concentration (r2 = 0.23; P = .026). CONCLUSIONS: Plasma Bilirubin Binding avidity contributes significantly to ΔBT. This component of ΔBT is associated with a lower risk of Bilirubin neurotoxicity, and studies aimed at incorporating plasma Bilirubin Binding avidity measurements into the algorithms used for management of newborn jaundice seem warranted.
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factors affecting the Binding of Bilirubin to serum albumins validation and application of the peroxidase method
Pediatric Research, 2006Co-Authors: Leslye Roca, Charles E. Ahlfors, Richard Wennberg, Sebastian Calligaris, Safarina G Malik, Donald J Ostrow, Claudio TiribelliAbstract:The unbound “free” Bilirubin concentration (Bf), not the total Bilirubin concentration, is the critical determinant of cellular uptake and toxicity of Bilirubin. We compared Bf measured by a modified peroxidase method with published data obtained with ultrafiltration and examined conditions that affect the affinity (KF) of human (HSA) and bovine (BSA) serum albumin for Bilirubin. The peroxidase and ultrafiltration methods yielded similar KF values that decreased with increasing HSA concentration and the presence of 50 mM chloride. When related to ionic strength, inhibition of BSA-Bilirubin Binding by chloride, bromide, and sulfate were similar, whereas phosphate buffer had a smaller effect. KF was lower at 37°C than at 25°C for HSA but not for BSA. KF for BSA was similar at pH 7.4 and 8.0. BSA and FCS had similar Binding properties. The close agreement of Bf and KF values determined by the peroxidase method with published results obtained by ultrafiltration validates both methods and supports the use of the peroxidase method as a practical technique for measuring Bf under steady state conditions in minimally diluted serum or culture medium.
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factors affecting the Binding of Bilirubin to serum albumins validation and application of the peroxidase method
Pediatric Research, 2006Co-Authors: Leslye Roca, Charles E. Ahlfors, Richard Wennberg, Sebastian Calligaris, Safarina G Malik, Donald J Ostrow, Claudio TiribelliAbstract:The unbound "free" Bilirubin concentration (Bf), not the total Bilirubin concentration, is the critical determinant of cellular uptake and toxicity of Bilirubin. We compared Bf measured by a modified peroxidase method with published data obtained with ultrafiltration and examined conditions that affect the affinity (KF) of human (HSA) and bovine (BSA) serum albumin for Bilirubin. The peroxidase and ultrafiltration methods yielded similar KF values that decreased with increasing HSA concentration and the presence of 50 mM chloride. When related to ionic strength, inhibition of BSA-Bilirubin Binding by chloride, bromide, and sulfate were similar, whereas phosphate buffer had a smaller effect. KF was lower at 37 degrees C than at 25 degrees C for HSA but not for BSA. KF for BSA was similar at pH 7.4 and 8.0. BSA and FCS had similar Binding properties. The close agreement of Bf and KF values determined by the peroxidase method with published results obtained by ultrafiltration validates both methods and supports the use of the peroxidase method as a practical technique for measuring Bf under steady state conditions in minimally diluted serum or culture medium.
Claudio Tiribelli - One of the best experts on this subject based on the ideXlab platform.
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factors affecting the Binding of Bilirubin to serum albumins validation and application of the peroxidase method
Pediatric Research, 2006Co-Authors: Leslye Roca, Charles E. Ahlfors, Richard Wennberg, Sebastian Calligaris, Safarina G Malik, Donald J Ostrow, Claudio TiribelliAbstract:The unbound "free" Bilirubin concentration (Bf), not the total Bilirubin concentration, is the critical determinant of cellular uptake and toxicity of Bilirubin. We compared Bf measured by a modified peroxidase method with published data obtained with ultrafiltration and examined conditions that affect the affinity (KF) of human (HSA) and bovine (BSA) serum albumin for Bilirubin. The peroxidase and ultrafiltration methods yielded similar KF values that decreased with increasing HSA concentration and the presence of 50 mM chloride. When related to ionic strength, inhibition of BSA-Bilirubin Binding by chloride, bromide, and sulfate were similar, whereas phosphate buffer had a smaller effect. KF was lower at 37 degrees C than at 25 degrees C for HSA but not for BSA. KF for BSA was similar at pH 7.4 and 8.0. BSA and FCS had similar Binding properties. The close agreement of Bf and KF values determined by the peroxidase method with published results obtained by ultrafiltration validates both methods and supports the use of the peroxidase method as a practical technique for measuring Bf under steady state conditions in minimally diluted serum or culture medium.
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factors affecting the Binding of Bilirubin to serum albumins validation and application of the peroxidase method
Pediatric Research, 2006Co-Authors: Leslye Roca, Charles E. Ahlfors, Richard Wennberg, Sebastian Calligaris, Safarina G Malik, Donald J Ostrow, Claudio TiribelliAbstract:The unbound “free” Bilirubin concentration (Bf), not the total Bilirubin concentration, is the critical determinant of cellular uptake and toxicity of Bilirubin. We compared Bf measured by a modified peroxidase method with published data obtained with ultrafiltration and examined conditions that affect the affinity (KF) of human (HSA) and bovine (BSA) serum albumin for Bilirubin. The peroxidase and ultrafiltration methods yielded similar KF values that decreased with increasing HSA concentration and the presence of 50 mM chloride. When related to ionic strength, inhibition of BSA-Bilirubin Binding by chloride, bromide, and sulfate were similar, whereas phosphate buffer had a smaller effect. KF was lower at 37°C than at 25°C for HSA but not for BSA. KF for BSA was similar at pH 7.4 and 8.0. BSA and FCS had similar Binding properties. The close agreement of Bf and KF values determined by the peroxidase method with published results obtained by ultrafiltration validates both methods and supports the use of the peroxidase method as a practical technique for measuring Bf under steady state conditions in minimally diluted serum or culture medium.
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bilitranslocase and sulfobromophthalein Bilirubin Binding protein are both involved in the hepatic uptake of organic anions
Proceedings of the National Academy of Sciences of the United States of America, 1993Co-Authors: Adriana M Torres, W Stremmel, Gian Carlo Lunazzi, Claudio TiribelliAbstract:Abstract The hepatic uptake of cholephilic organic anions is a carrier-mediated process. Three distinct proteins [bilitranslocase (BTL), sulfobromophthalein (BSP)/Bilirubin-Binding protein (BBBP), and organic anion-Binding protein] have been isolated from the basolateral plasma-membrane domain of the hepatocyte. To investigate the relative role of the first two of them in accounting for the hepatic uptake of organic anions, we measured the initial rates of uptake of 35S-labeled BSP into rat liver plasma-membrane vesicles. Because transport by BTL is electrogenic but transport by BBBP is electroneutral, studies were done either with or without a positive-inside membrane potential produced by adding valinomycin in the presence of an inwardly directed K+ gradient (outside K+ > inside K+). Both electrogenic and electroneutral transport systems followed saturation kinetics. Electroneutral uptake showed an apparent Km of 20 +/- 3 microM (mean +/- SD) and a Vmax of 1.0 +/- 0.13 nmol.(mg of prot)-1.15 sec-1, whereas the electrogenic portion of BSP uptake exhibited a Km of 5.2 +/- 0.8 microM and a Vmax of 1.1 +/- 0.1 nmol.(mg of prot)-1.15 sec-1. In this case, an overshoot was observed 15 sec after valinomycin addition. Electroneutral BSP uptake was inhibited by incubation with anti-BBBP antibody, whereas anti-BTL antibody did not show any inhibitory effect. Conversely, the electrogenic uptake was inhibited by anti-BTL antibody at a BSP concentration of 5 microM; no inhibition was seen either at 20 microM BSP or upon addition of anti-BBBP antibody. From these data we conclude that the hepatic uptake of organic ions occurs via two immunologically distinct carrier proteins (BTL and BBBP) operating in parallel. BTL is a higher affinity electrogenic transporting system of organic ions, whereas BBBP is a lower affinity electroneutral transporter.
Angelo A. Lamola - One of the best experts on this subject based on the ideXlab platform.
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a multi center evaluation of a device for measurement of Bilirubin Binding capacity in neonates the effects of gestational age intralipid exposure and illness severity
Journal of Perinatology, 2019Co-Authors: David L Schutzman, Angelo A. Lamola, Vinod K Bhutani, Martin Castillo E Cuadrado, Ivan D Frantz, Evelyn Obregon, Ronald J WongAbstract:Measure daily Bilirubin-Binding capacity (BBC) variation using an automated, not as-yet FDA approved, Point-of-Care hematofluorometer. Measure the effects of prematurity, clinical instability and exposure to Intralipid on BBC. Convenience sample of 109 infants from well-baby and intensive care nurseries. Gestational ages 28–41 weeks. 261 specimens obtained from postnatal ages 1–4 days. Unstable neonates were defined by need for at least noninvasive respiratory support and FiO2 ≥ 0.25. Median interday variation was 2.9 ± 5.1 mg/dL. BBC (0.254 mg/dL/wk) and albumin (0.037 g/dL/wk) increased for each week of gestation. BBC was lower in unstable compared to well infants (26.1 ± 7.6 mg/dL v 28.6 ± 6.3 mg/dL). BBC was not significantly different in infants receiving or not receiving IL. BBC measurements using the device had acceptable intraspecimen reproducibility and interday variability. BBC may be helpful in guiding the assessment of aggressive versus conservative management decisions in preterm and sick infants with hyperBilirubinemia.
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neonatal Bilirubin Binding capacity discerns risk of neurological dysfunction
Pediatric Research, 2015Co-Authors: Angelo A. Lamola, Ronald J Wong, Vinod K Bhutani, Martin Castillo E Cuadrado, Lihua Chen, Zheng Shen, David K StevensonAbstract:Bilirubin Binding capacity (BBC) defines the dynamic relationship between an infant’s level of unbound or “free” Bilirubin and his/her ability to “tolerate” increasing Bilirubin loads. BBC is not synonymous with albumin (Alb) levels because Alb Binding of Bilirubin is confounded by a variety of molecular, biologic, and metabolic factors. We utilized a novel modification of a previously developed hematofluorometric method to directly assay BBC in whole blood from preterm and term neonates and then combined these data with an archived database. Total Bilirubin (TB) was also measured, and multiple regression modeling was used to determine whether BBC in combination with TB measurements can assess an infant’s risk for developing Bilirubin-induced neurotoxicity. TB and BBC levels ranged from 0.7–22.8 to 6.3–47.5 mg/dl, respectively. Gestational age (GA) correlated with BBC (r = 0.54; P < 0.0002) with a slope of 0.93 mg/dl/wk by logistic regression. Our calculations demonstrate that recently recommended GA-modulated TB thresholds for phototherapy and exchange transfusion correspond to 45 and 67% saturation of our observed regression line, respectively. We speculate that the spread of BBC levels around the regression line (±5.8 mg/dl) suggests that individualized BBC assays would provide a robust approach to gauge risk of Bilirubin neurotoxicity compared with TB and GA.
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Newborn Jaundice Technologies: Unbound Bilirubin and Bilirubin Binding Capacity in Neonates
Seminars in perinatology, 2011Co-Authors: Sanjiv B. Amin, Angelo A. LamolaAbstract:Neonatal jaundice (hyperBilirubinemia), which is extremely common in neonates, can be associated with neurotoxicity. A safe level of Bilirubin has not been defined in either premature or term infants. Emerging evidence suggest that the level of unbound (or "free") Bilirubin has a better sensitivity and specificity than total serum Bilirubin for Bilirubin-induced neurotoxicity. Although recent studies suggest the usefulness of free Bilirubin measurements in managing high-risk neonates, including premature infants, no widely available method exists to assay the serum free Bilirubin concentration. To keep pace with the growing demand, in addition to reevaluation of old methods, several promising new methods are being developed for sensitive, accurate, and rapid measurement of free Bilirubin and Bilirubin Binding capacity. These innovative methods need to be validated before adopting for clinical use. We provide an overview of some promising methods for free Bilirubin and Binding capacity measurements with the goal to enhance research in this area of active interest and apparent need.