The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Frank Thévenod - One of the best experts on this subject based on the ideXlab platform.
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abcb1 protects Kidney Proximal Tubule cells against cadmium induced apoptosis roles of cadmium and ceramide transport
Toxicological Sciences, 2011Co-Authors: Wing-kee Lee, Blazej Torchalski, Naschla Kohistani, Frank ThévenodAbstract:Cadmium (Cd(2+)) damages the Kidney Proximal Tubule (PT) by ceramide-dependent apoptosis and is also a class I carcinogen. Multidrug resistance P-glycoprotein (MDR1, ABCB1) confers resistance to Cd(2+) apoptosis, and it has been hypothesized that ABCB1 can directly transport Cd(2+) as a mode of cellular protection. Our aim was to investigate the role of ABCB1 in Cd(2+) transport and ceramide apoptosis. In rat PT or Madin-Darby canine Kidney (MDCK) cells overexpressing ABCB1, ABCB1-dependent efflux of rhodamine 123(+) (Rh123(+)) or (109)Cd(2+) were determined, and cell death was assayed with MTT, H-33342 nuclear staining, and monolayer integrity by impedance sensing (Electric cell-substrate impedance sensing [ECIS]). ABCB1 inhibitors (PSC833, UIC-2 antibody) did not affect (109)Cd(2+) efflux in PT cells though Rh123(+) transport was blocked. Furthermore, increased ABCB1 expression did not augment (109)Cd(2+) efflux but attenuated apoptosis by 10-50μM Cd(2+) or 5-25μM C(6)-ceramide, which was abolished by PSC833 (1μM). ECIS measurements of ABCB1-MDCK monolayers exhibited similar effects. Moreover, in ABCB1-MDCK cells, Cd(2+)-induced ceramide formation, determined by a diacylglycerol kinase assay, was abolished and increased extrusion of nitro-2-1,3-benzoxadiazol-4-yl (NBD)-C(6)-ceramide, and NBD-C(6)-glucosylceramide was observed compared with MDCK cells. Whereas pharmacological block of sphingomyelin synthase (0.1mM D609) or sphingosine kinase (1μM dimethylsphingosine), which increase the levels of ceramide and its metabolites, augmented Cd(2+)-induced apoptosis, Cd(2+) apoptosis was significantly decreased not only by prevention of de novo ceramide synthesis (0.1μM fumonisin B(1)) but also by inhibition of glucosylceramide synthase (2μM C(9)DGJ). We therefore conclude that Cd(2+) efflux is not the mechanism behind ABCB1-mediated protection from Cd(2+) apoptosis. Rather, the sphingolipid glucosylceramide may be the proapoptotic substrate extruded by ABCB1.
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Ferroportin 1 is expressed basolaterally in rat Kidney Proximal Tubule cells and iron excess increases its membrane trafficking
Journal of cellular and molecular medicine, 2011Co-Authors: Natascha A. Wolff, Wing-kee Lee, Frank Thévenod, Wei Liu, Robert A. Fenton, Craig P. SmithAbstract:Ferroportin 1 (FPN1) is an iron export protein expressed in liver and duodenum, as well as in reticuloendothelial macrophages. Previously, we have shown that divalent metal transporter 1 (DMT1) is expressed in late endosomes and lysosomes of the Kidney Proximal Tubule (PT), the nephron segment responsible for the majority of solute reabsorption. We suggested that following receptor mediated endocytosis of transferrin filtered by the glomerulus, DMT1 exports iron liberated from transferrin into the cytosol. FPN1 is also expressed in the Kidney yet its role remains obscure. As a first step towards determining the role of renal FPN1, we localized FPN1 in the PT. FPN1 was found to be located in association with the basolateral PT membrane and within the cytosolic compartment. FPN1 was not expressed on the apical brush-border membrane of PT cells. These data support a role for FPN1 in vectorial export of iron out of PT cells. Furthermore, under conditions of iron loading of cultured PT cells, FPN1 was trafficked to the plasma membrane suggesting a coordinated cellular response to export excess iron and limit cellular iron concentrations.
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novel roles for ceramides calpains and caspases in Kidney Proximal Tubule cell apoptosis lessons from in vitro cadmium toxicity studies
Biochemical Pharmacology, 2008Co-Authors: Wing-kee Lee, Frank ThévenodAbstract:Apoptosis is a tightly regulated physiological process, which can be initiated by toxic stimuli, such as cadmium (Cd2+). Cd2+ (10-50 microM) induces a rapid increase in reactive oxygen species (ROS) (> or = 30 min) in a cell line derived from the S1 segment of rat Kidney Proximal Tubule, without any apparent mitochondrial dysfunction. The sphingolipid ceramide is an important second messenger in apoptosis. Short exposure to Cd2+ (3h) causes an increase in ceramides, which occurs downstream of ROS formation, and may interact with cellular components, such as endoplasmic reticulum and mitochondria. Following apoptosis initiation, execution must take place. The classical executioners of apoptosis are caspases, a family of cysteine proteases. However, increasing studies report caspase-independent apoptosis, which questions the essentiality of caspases for apoptosis implementation. With low micromolar Cd2+ concentrations (< 10 microM), caspases are only activated after 24h and not at earlier time points, which supports the notion of caspase-independent apoptosis. Due to increased cytosolic Ca(2+) under pathological conditions, a role for the Ca2+-dependent proteases, calpains, has emerged. Calpain activation by Cd2+ (3-6h) seems to be regulated by ceramide levels, in order to induce apoptosis. Calpain and caspase substrates overlap but yield different fragments, which may explain their diverse downstream targets. Furthermore, calpains and caspases may interact with one another to enhance, as seen by Cd2+, or diminish apoptosis. In this review, we discuss novel roles for ceramides, calpains and caspases as part of Cd2+-induced apoptotic signalling pathways in the Kidney Proximal Tubule and their in vivo relevance to Cd2+-induced nephrotoxicity.
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Novel roles for ceramides, calpains and caspases in Kidney Proximal Tubule cell apoptosis: lessons from in vitro cadmium toxicity studies.
Biochemical pharmacology, 2008Co-Authors: Wing-kee Lee, Frank ThévenodAbstract:Apoptosis is a tightly regulated physiological process, which can be initiated by toxic stimuli, such as cadmium (Cd2+). Cd2+ (10–50 μM) induces a rapid increase in reactive oxygen species (ROS) (≥30 min) in a cell line derived from the S1 segment of rat Kidney Proximal Tubule, without any apparent mitochondrial dysfunction. The sphingolipid ceramide is an important second messenger in apoptosis. Short exposure to Cd2+ (3 h) causes an increase in ceramides, which occurs downstream of ROS formation, and may interact with cellular components, such as endoplasmic reticulum and mitochondria. Following apoptosis initiation, execution must take place. The classical executioners of apoptosis are caspases, a family of cysteine proteases. However, increasing studies report caspase-independent apoptosis, which questions the essentiality of caspases for apoptosis implementation. With low micromolar Cd2+ concentrations (
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Cadmium-induced ceramide formation triggers calpain-dependent apoptosis in cultured Kidney Proximal Tubule cells
American journal of physiology. Cell physiology, 2007Co-Authors: Wing-kee Lee, Blazej Torchalski, Frank ThévenodAbstract:A major target of cadmium (Cd2+) toxicity is the Kidney Proximal Tubule (PT) cell. Cd2+-induced apoptosis of PT cells is mediated by sequential activation of calpains at 3–6 h and caspases-9 and -3...
Wing-kee Lee - One of the best experts on this subject based on the ideXlab platform.
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abcb1 protects Kidney Proximal Tubule cells against cadmium induced apoptosis roles of cadmium and ceramide transport
Toxicological Sciences, 2011Co-Authors: Wing-kee Lee, Blazej Torchalski, Naschla Kohistani, Frank ThévenodAbstract:Cadmium (Cd(2+)) damages the Kidney Proximal Tubule (PT) by ceramide-dependent apoptosis and is also a class I carcinogen. Multidrug resistance P-glycoprotein (MDR1, ABCB1) confers resistance to Cd(2+) apoptosis, and it has been hypothesized that ABCB1 can directly transport Cd(2+) as a mode of cellular protection. Our aim was to investigate the role of ABCB1 in Cd(2+) transport and ceramide apoptosis. In rat PT or Madin-Darby canine Kidney (MDCK) cells overexpressing ABCB1, ABCB1-dependent efflux of rhodamine 123(+) (Rh123(+)) or (109)Cd(2+) were determined, and cell death was assayed with MTT, H-33342 nuclear staining, and monolayer integrity by impedance sensing (Electric cell-substrate impedance sensing [ECIS]). ABCB1 inhibitors (PSC833, UIC-2 antibody) did not affect (109)Cd(2+) efflux in PT cells though Rh123(+) transport was blocked. Furthermore, increased ABCB1 expression did not augment (109)Cd(2+) efflux but attenuated apoptosis by 10-50μM Cd(2+) or 5-25μM C(6)-ceramide, which was abolished by PSC833 (1μM). ECIS measurements of ABCB1-MDCK monolayers exhibited similar effects. Moreover, in ABCB1-MDCK cells, Cd(2+)-induced ceramide formation, determined by a diacylglycerol kinase assay, was abolished and increased extrusion of nitro-2-1,3-benzoxadiazol-4-yl (NBD)-C(6)-ceramide, and NBD-C(6)-glucosylceramide was observed compared with MDCK cells. Whereas pharmacological block of sphingomyelin synthase (0.1mM D609) or sphingosine kinase (1μM dimethylsphingosine), which increase the levels of ceramide and its metabolites, augmented Cd(2+)-induced apoptosis, Cd(2+) apoptosis was significantly decreased not only by prevention of de novo ceramide synthesis (0.1μM fumonisin B(1)) but also by inhibition of glucosylceramide synthase (2μM C(9)DGJ). We therefore conclude that Cd(2+) efflux is not the mechanism behind ABCB1-mediated protection from Cd(2+) apoptosis. Rather, the sphingolipid glucosylceramide may be the proapoptotic substrate extruded by ABCB1.
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Ferroportin 1 is expressed basolaterally in rat Kidney Proximal Tubule cells and iron excess increases its membrane trafficking
Journal of cellular and molecular medicine, 2011Co-Authors: Natascha A. Wolff, Wing-kee Lee, Frank Thévenod, Wei Liu, Robert A. Fenton, Craig P. SmithAbstract:Ferroportin 1 (FPN1) is an iron export protein expressed in liver and duodenum, as well as in reticuloendothelial macrophages. Previously, we have shown that divalent metal transporter 1 (DMT1) is expressed in late endosomes and lysosomes of the Kidney Proximal Tubule (PT), the nephron segment responsible for the majority of solute reabsorption. We suggested that following receptor mediated endocytosis of transferrin filtered by the glomerulus, DMT1 exports iron liberated from transferrin into the cytosol. FPN1 is also expressed in the Kidney yet its role remains obscure. As a first step towards determining the role of renal FPN1, we localized FPN1 in the PT. FPN1 was found to be located in association with the basolateral PT membrane and within the cytosolic compartment. FPN1 was not expressed on the apical brush-border membrane of PT cells. These data support a role for FPN1 in vectorial export of iron out of PT cells. Furthermore, under conditions of iron loading of cultured PT cells, FPN1 was trafficked to the plasma membrane suggesting a coordinated cellular response to export excess iron and limit cellular iron concentrations.
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novel roles for ceramides calpains and caspases in Kidney Proximal Tubule cell apoptosis lessons from in vitro cadmium toxicity studies
Biochemical Pharmacology, 2008Co-Authors: Wing-kee Lee, Frank ThévenodAbstract:Apoptosis is a tightly regulated physiological process, which can be initiated by toxic stimuli, such as cadmium (Cd2+). Cd2+ (10-50 microM) induces a rapid increase in reactive oxygen species (ROS) (> or = 30 min) in a cell line derived from the S1 segment of rat Kidney Proximal Tubule, without any apparent mitochondrial dysfunction. The sphingolipid ceramide is an important second messenger in apoptosis. Short exposure to Cd2+ (3h) causes an increase in ceramides, which occurs downstream of ROS formation, and may interact with cellular components, such as endoplasmic reticulum and mitochondria. Following apoptosis initiation, execution must take place. The classical executioners of apoptosis are caspases, a family of cysteine proteases. However, increasing studies report caspase-independent apoptosis, which questions the essentiality of caspases for apoptosis implementation. With low micromolar Cd2+ concentrations (< 10 microM), caspases are only activated after 24h and not at earlier time points, which supports the notion of caspase-independent apoptosis. Due to increased cytosolic Ca(2+) under pathological conditions, a role for the Ca2+-dependent proteases, calpains, has emerged. Calpain activation by Cd2+ (3-6h) seems to be regulated by ceramide levels, in order to induce apoptosis. Calpain and caspase substrates overlap but yield different fragments, which may explain their diverse downstream targets. Furthermore, calpains and caspases may interact with one another to enhance, as seen by Cd2+, or diminish apoptosis. In this review, we discuss novel roles for ceramides, calpains and caspases as part of Cd2+-induced apoptotic signalling pathways in the Kidney Proximal Tubule and their in vivo relevance to Cd2+-induced nephrotoxicity.
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Novel roles for ceramides, calpains and caspases in Kidney Proximal Tubule cell apoptosis: lessons from in vitro cadmium toxicity studies.
Biochemical pharmacology, 2008Co-Authors: Wing-kee Lee, Frank ThévenodAbstract:Apoptosis is a tightly regulated physiological process, which can be initiated by toxic stimuli, such as cadmium (Cd2+). Cd2+ (10–50 μM) induces a rapid increase in reactive oxygen species (ROS) (≥30 min) in a cell line derived from the S1 segment of rat Kidney Proximal Tubule, without any apparent mitochondrial dysfunction. The sphingolipid ceramide is an important second messenger in apoptosis. Short exposure to Cd2+ (3 h) causes an increase in ceramides, which occurs downstream of ROS formation, and may interact with cellular components, such as endoplasmic reticulum and mitochondria. Following apoptosis initiation, execution must take place. The classical executioners of apoptosis are caspases, a family of cysteine proteases. However, increasing studies report caspase-independent apoptosis, which questions the essentiality of caspases for apoptosis implementation. With low micromolar Cd2+ concentrations (
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Cadmium-induced ceramide formation triggers calpain-dependent apoptosis in cultured Kidney Proximal Tubule cells
American journal of physiology. Cell physiology, 2007Co-Authors: Wing-kee Lee, Blazej Torchalski, Frank ThévenodAbstract:A major target of cadmium (Cd2+) toxicity is the Kidney Proximal Tubule (PT) cell. Cd2+-induced apoptosis of PT cells is mediated by sequential activation of calpains at 3–6 h and caspases-9 and -3...
Mary Taub - One of the best experts on this subject based on the ideXlab platform.
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Response of primary rabbit Kidney Proximal Tubule cells to estrogens
Journal of cellular physiology, 1999Co-Authors: Ho Jae Han, Jee Chang Jung, Mary TaubAbstract:The effects of estrogens on the growth and function of primary rabbit Kidney Proximal Tubule (RPT) cells have been examined in hormonally defined phenol red-free medium. 17beta-estradiol was observed to stimulate growth at dosages as low as 10(-10) M. The growth stimulatory effects of 17beta-estradiol were mitigated in the presence of hydrocortisone, suggesting that these two steroid hormones acted at least in part by common mechanisms. The effects of other steroids known to interact with the estrogen receptor were examined. Alpha estradiol was found to be growth stimulatory over a concentration range of 10(-9) to 10(-8) M, albeit to a lower extent than beta estradiol. In addition, the anti-estrogen tamoxifen was also growth stimulatory (unlike the case with the human mammary tumor cell line MCF-7). The effects of several metabolic precursors of 17beta-estradiol were examined, including testosterone, which was growth stimulatory, and progesterone, which was growth inhibitory. The growth stimulatory effects of 17beta-estradiol, alpha estradiol, and tamoxifen could possibly be explained by their interaction with an estrogen receptor. Indeed, metabolic labelling and immunoprecipitation studies indicated the presence of such an estrogen receptor in the primary cultures. The rate of biosynthesis of the estrogen receptor was found to be affected by the presence of exogenously added 17beta-estradiol. 17beta-estradiol was also observed to increase the activity of two brush border enzymes, alkaline phosphatase and gamma glutamyl transpeptidase, during the growth phase of the primary cultures.
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Growth and function of primary rabbit Kidney Proximal Tubule cells in glucose-free serum-free medium.
Journal of cellular physiology, 1992Co-Authors: Jee Chang Jung, Sang‐mog Lee, Nina Kadakia, Mary TaubAbstract:The properties of primary rabbit Kidney Proximal Tubule cells in glucose-free serum-free medium have been examined. Primary rabbit Kidney Proximal Tubule cells were observed to grow at the same rate, 1.0 doublings/day, both in glucose-free and in glucose-supplemented medium. Growth in glucose-free medium was dependent upon the presence of an additional nutritional supplement, such as glutamine, pyruvate, palmitate, lactate, or beta hydroxybutyrate. Lactate, pyruvate, and glutamate are utilized for renal gluconeogenesis in vivo. The growth of the primary rabbit Kidney Proximal Tubule cells in glucose-free medium was also dependent upon the presence of the three growth supplements insulin, transferrin, and hydrocortisone. Insulin was growth stimulatory to the primary Proximal Tubule cells in glucose-free medium, although insulin causes a reduction in the phosphoenolpyruvate carboxykinase (PEPCK) activity in these cells. PEPCK is a key regulatory enzyme in the gluconeogenic pathway. In order to evaluate whether or not the primary cells have gluconeogenic capacity, their glucose content was determined. The cells contained 5 pmoles D-glucose/mg protein. However, no significant glucose was detected in the medium. Presumably, the primary cells were either utilizing or storing the glucose made by the gluconeogenic pathway. Consistent with this latter possibility, cellular glycogen levels were observed to increase with time in culture. The effect of glucose on the expression of the alpha I(IV) collagen and laminin B1 chain genes was examined. Northern analysis indicated that the level of alpha I(IV) collagen mRNA was significantly elevated in glucose containing, as compared with glucose deficient, medium. In contrast, laminin B1 chain mRNA levels were not significantly affected by the glucose content of the medium.
Jee Chang Jung - One of the best experts on this subject based on the ideXlab platform.
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Response of primary rabbit Kidney Proximal Tubule cells to estrogens
Journal of cellular physiology, 1999Co-Authors: Ho Jae Han, Jee Chang Jung, Mary TaubAbstract:The effects of estrogens on the growth and function of primary rabbit Kidney Proximal Tubule (RPT) cells have been examined in hormonally defined phenol red-free medium. 17beta-estradiol was observed to stimulate growth at dosages as low as 10(-10) M. The growth stimulatory effects of 17beta-estradiol were mitigated in the presence of hydrocortisone, suggesting that these two steroid hormones acted at least in part by common mechanisms. The effects of other steroids known to interact with the estrogen receptor were examined. Alpha estradiol was found to be growth stimulatory over a concentration range of 10(-9) to 10(-8) M, albeit to a lower extent than beta estradiol. In addition, the anti-estrogen tamoxifen was also growth stimulatory (unlike the case with the human mammary tumor cell line MCF-7). The effects of several metabolic precursors of 17beta-estradiol were examined, including testosterone, which was growth stimulatory, and progesterone, which was growth inhibitory. The growth stimulatory effects of 17beta-estradiol, alpha estradiol, and tamoxifen could possibly be explained by their interaction with an estrogen receptor. Indeed, metabolic labelling and immunoprecipitation studies indicated the presence of such an estrogen receptor in the primary cultures. The rate of biosynthesis of the estrogen receptor was found to be affected by the presence of exogenously added 17beta-estradiol. 17beta-estradiol was also observed to increase the activity of two brush border enzymes, alkaline phosphatase and gamma glutamyl transpeptidase, during the growth phase of the primary cultures.
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Angiotensin II-mediated stimulation of phospholipase D in rabbit Kidney Proximal Tubule cells.
Archives of Pharmacal Research, 1994Co-Authors: Jin-ho Jung, Jee Chang Jung, Sung Hyun ChungAbstract:The present study was undertaken to demonstrate whether or not angiotensin II activates a phospholipase D in rabbit Kidney Proximal Tubule cells. By measuring the formation of [3H]phosphatidic acid and [3H]phosphatidylethanol, we elucidate the direct stimulation of phospholipase D by angiotensin II. Angiotensin II leads to a rapid increase in [3H]phosphatidic acid and [3H]diacylglycerol, and [3H]phosphatidic acid formation preceeded the formation of [3H]diacylglycerol. This result suggests that some phosphatidic acid seems to be formed directly from phosphatidylcholine by the action of phospholipase D, not from the action of diacylglycerol kinase on the diacylglycerol. In addition, the other mechanisms by which phospholipase D is activated was examined. We have found that phospholipase D was activated by extracellular calcium ion. It has also been shown that angiotensin II may activate phospholipase D through protein kinase C-independent pathway.
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Growth and function of primary rabbit Kidney Proximal Tubule cells in glucose-free serum-free medium.
Journal of cellular physiology, 1992Co-Authors: Jee Chang Jung, Sang‐mog Lee, Nina Kadakia, Mary TaubAbstract:The properties of primary rabbit Kidney Proximal Tubule cells in glucose-free serum-free medium have been examined. Primary rabbit Kidney Proximal Tubule cells were observed to grow at the same rate, 1.0 doublings/day, both in glucose-free and in glucose-supplemented medium. Growth in glucose-free medium was dependent upon the presence of an additional nutritional supplement, such as glutamine, pyruvate, palmitate, lactate, or beta hydroxybutyrate. Lactate, pyruvate, and glutamate are utilized for renal gluconeogenesis in vivo. The growth of the primary rabbit Kidney Proximal Tubule cells in glucose-free medium was also dependent upon the presence of the three growth supplements insulin, transferrin, and hydrocortisone. Insulin was growth stimulatory to the primary Proximal Tubule cells in glucose-free medium, although insulin causes a reduction in the phosphoenolpyruvate carboxykinase (PEPCK) activity in these cells. PEPCK is a key regulatory enzyme in the gluconeogenic pathway. In order to evaluate whether or not the primary cells have gluconeogenic capacity, their glucose content was determined. The cells contained 5 pmoles D-glucose/mg protein. However, no significant glucose was detected in the medium. Presumably, the primary cells were either utilizing or storing the glucose made by the gluconeogenic pathway. Consistent with this latter possibility, cellular glycogen levels were observed to increase with time in culture. The effect of glucose on the expression of the alpha I(IV) collagen and laminin B1 chain genes was examined. Northern analysis indicated that the level of alpha I(IV) collagen mRNA was significantly elevated in glucose containing, as compared with glucose deficient, medium. In contrast, laminin B1 chain mRNA levels were not significantly affected by the glucose content of the medium.
Teresa F. Moura - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Properties of Brush Border Membrane Vesicles from Kidney Proximal Tubule
The Journal of membrane biology, 1997Co-Authors: Graça Soveral, Robert I. Macey, Teresa F. MouraAbstract:The mechanical properties of brush border membrane vesicles, BBMV, from rabbit Kidney Proximal Tubule cells, were studied by measuring the initial and final equilibrium volumes of vesicles subjected to different osmotic shocks, using cellobiose as the impermeant solute in the preparation buffer.
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Membrane stress causes inhibition of water channels in brush border membrane vesicles from Kidney Proximal Tubule
Biology of the cell, 1997Co-Authors: Graça Soveral, Robert I. Macey, Teresa F. MouraAbstract:Brush border membrane vesicles (BBMV) from rabbit Kidney Proximal Tubule cells, prepared with different internal solute concentrations (cellobiose buffer 13, 18 or 85 mosM) developed an hydrostatic pressure difference across the membrane of 18.7 mosM, that causes a membrane tension close to 5 × 10−5 N cm−1. When subjected to several hypertonic osmotic shocks an initial delay of osmotic shrinkage (a lag time), corresponding to a very small change in initial volume was apparent. This initial osmotic response, which is significantly retarded, was correlated with the initial period of elevated membrane tension, suggesting that the water permeability coefficient is inhibited by membrane stress. We speculate that this inhibition may serve to regulate cell volume in the Proximal Tubule.
