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M G Collis - One of the best experts on this subject based on the ideXlab platform.
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pharmacokinetics of 8 Phenyltheophylline in the rat
Journal of Pharmacy and Pharmacology, 2011Co-Authors: A Wormald, M. S. Yates, Christopher J. Bowmer, M G CollisAbstract:The pharmacokinetics of the adenosine antagonist 8-Phenyltheophylline (8-PT) have been investigated in the rat. After intravenous administration to male rats with normal renal function, 8-PT was rapidly cleared from plasma with a t1/2 of about 14 min. Its apparent volume of distribution was some 76 mL/100 g and plasma clearance was 3.5 mL min-1/100 g. Injection via the carotid artery did not alter the kinetics of 8-PT, but when given through the portal vein a first-pass effect was observed. Moreover, 8-PT could not be detected in plasma following intraperitoneal injection. The kinetics of 8-PT were not altered in male rats with acute renal failure and no difference was noted between male and female animals with respect to the kinetics of 8-PT following intravenous injection. It is concluded that the pharmacokinetic properties of 8-PT are likely to complicate its use in-vivo.
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comparison of the potency of 8 Phenyltheophylline as an antagonist at a1 and a2 adenosine receptors in atria and aorta from the guinea pig
Journal of Pharmacy and Pharmacology, 2011Co-Authors: M G Collis, D B Palmer, V L SavilleAbstract:The potency of 8−Phenyltheophylline as an antagonist at A, adenosine receptors in guinea-pig atria and at A2 adenosine receptors in the guinea-pig aorta has been investigated. 8-Phenyltheophylfine was an apparently competitive antagonist of the negative chronotropic effect of adenosine, 2-chloroadenosine, L- N6 -phenyl-isopropyl adenosine (L-PIA) and 5′- N-ethylcarboxamide adenosine (NECA) on atria and of the relaxant effect of adenosine, 2−chloroadenosine and NECA on the aorta. The pA2 values for 8−Phenyltheophylline ranged from 6.4 to 6.6 and were not significantly different, irrespective of the agonist or tissue used. These results indicate that 8−Phenyltheophylline is a relatively potent antagonist at adenosine receptors but does not exhibit selectivity for either of the putative sub-types in isolated tissues.
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amelioration of glycerol induced acute renal failure in the rat with 8 Phenyltheophylline timing of intervention
Journal of Pharmacy and Pharmacology, 2011Co-Authors: Christopher J. Bowmer, M G Collis, M. S. YatesAbstract:The importance of timing and duration of 8-Phenyltheophylline (8-PT) administration in determining its beneficial action in glycerol-induced acute renal failure (ARF) was investigated by examining the effects of a single dose of 8-PT given immediately following (0 h) glycerol injection and at 1 and 3 h after glycerol injection. 8-PT when given at 0 h significantly lowered plasma urea and creatinine concentrations and significantly increased inulin clearance when compared both to untreated animals and those that received the vehicle for the drug. By contrast, 8-PT when administered at 1 h afforded no protective effect on renal function and, when injected at 3 h, the only significant effect was lowered plasma creatinine levels when compared to untreated rats; at this latter time it did not lower plasma urea levels or improve inulin clearance. None of the 8-PT injections attenuated the increase in kidney weight associated with ARF or reduced the kidney damage as assessed by histological examination. The results show that a single administration of 8-PT made immediately following glycerol injection can ameliorate the biochemical and functional indices of impaired renal function, but does not produce an improvement in kidney morphology.
M. S. Yates - One of the best experts on this subject based on the ideXlab platform.
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pharmacokinetics of 8 Phenyltheophylline in the rat
Journal of Pharmacy and Pharmacology, 2011Co-Authors: A Wormald, M. S. Yates, Christopher J. Bowmer, M G CollisAbstract:The pharmacokinetics of the adenosine antagonist 8-Phenyltheophylline (8-PT) have been investigated in the rat. After intravenous administration to male rats with normal renal function, 8-PT was rapidly cleared from plasma with a t1/2 of about 14 min. Its apparent volume of distribution was some 76 mL/100 g and plasma clearance was 3.5 mL min-1/100 g. Injection via the carotid artery did not alter the kinetics of 8-PT, but when given through the portal vein a first-pass effect was observed. Moreover, 8-PT could not be detected in plasma following intraperitoneal injection. The kinetics of 8-PT were not altered in male rats with acute renal failure and no difference was noted between male and female animals with respect to the kinetics of 8-PT following intravenous injection. It is concluded that the pharmacokinetic properties of 8-PT are likely to complicate its use in-vivo.
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amelioration of glycerol induced acute renal failure in the rat with 8 Phenyltheophylline timing of intervention
Journal of Pharmacy and Pharmacology, 2011Co-Authors: Christopher J. Bowmer, M G Collis, M. S. YatesAbstract:The importance of timing and duration of 8-Phenyltheophylline (8-PT) administration in determining its beneficial action in glycerol-induced acute renal failure (ARF) was investigated by examining the effects of a single dose of 8-PT given immediately following (0 h) glycerol injection and at 1 and 3 h after glycerol injection. 8-PT when given at 0 h significantly lowered plasma urea and creatinine concentrations and significantly increased inulin clearance when compared both to untreated animals and those that received the vehicle for the drug. By contrast, 8-PT when administered at 1 h afforded no protective effect on renal function and, when injected at 3 h, the only significant effect was lowered plasma creatinine levels when compared to untreated rats; at this latter time it did not lower plasma urea levels or improve inulin clearance. None of the 8-PT injections attenuated the increase in kidney weight associated with ARF or reduced the kidney damage as assessed by histological examination. The results show that a single administration of 8-PT made immediately following glycerol injection can ameliorate the biochemical and functional indices of impaired renal function, but does not produce an improvement in kidney morphology.
Christopher J. Bowmer - One of the best experts on this subject based on the ideXlab platform.
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pharmacokinetics of 8 Phenyltheophylline in the rat
Journal of Pharmacy and Pharmacology, 2011Co-Authors: A Wormald, M. S. Yates, Christopher J. Bowmer, M G CollisAbstract:The pharmacokinetics of the adenosine antagonist 8-Phenyltheophylline (8-PT) have been investigated in the rat. After intravenous administration to male rats with normal renal function, 8-PT was rapidly cleared from plasma with a t1/2 of about 14 min. Its apparent volume of distribution was some 76 mL/100 g and plasma clearance was 3.5 mL min-1/100 g. Injection via the carotid artery did not alter the kinetics of 8-PT, but when given through the portal vein a first-pass effect was observed. Moreover, 8-PT could not be detected in plasma following intraperitoneal injection. The kinetics of 8-PT were not altered in male rats with acute renal failure and no difference was noted between male and female animals with respect to the kinetics of 8-PT following intravenous injection. It is concluded that the pharmacokinetic properties of 8-PT are likely to complicate its use in-vivo.
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amelioration of glycerol induced acute renal failure in the rat with 8 Phenyltheophylline timing of intervention
Journal of Pharmacy and Pharmacology, 2011Co-Authors: Christopher J. Bowmer, M G Collis, M. S. YatesAbstract:The importance of timing and duration of 8-Phenyltheophylline (8-PT) administration in determining its beneficial action in glycerol-induced acute renal failure (ARF) was investigated by examining the effects of a single dose of 8-PT given immediately following (0 h) glycerol injection and at 1 and 3 h after glycerol injection. 8-PT when given at 0 h significantly lowered plasma urea and creatinine concentrations and significantly increased inulin clearance when compared both to untreated animals and those that received the vehicle for the drug. By contrast, 8-PT when administered at 1 h afforded no protective effect on renal function and, when injected at 3 h, the only significant effect was lowered plasma creatinine levels when compared to untreated rats; at this latter time it did not lower plasma urea levels or improve inulin clearance. None of the 8-PT injections attenuated the increase in kidney weight associated with ARF or reduced the kidney damage as assessed by histological examination. The results show that a single administration of 8-PT made immediately following glycerol injection can ameliorate the biochemical and functional indices of impaired renal function, but does not produce an improvement in kidney morphology.
Gareth A Edwards - One of the best experts on this subject based on the ideXlab platform.
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activation of p1 and p2y purinoceptors by adp ribose in the guinea pig taenia coli but not of p2x purinoceptors in the vas deferens
British Journal of Pharmacology, 1992Co-Authors: Charles H V Hoyle, Gareth A EdwardsAbstract:1. The activity of adenosine 5'-diphosphoribose (ADP-ribose), a ribosylated purine nucleotide, was investigated on the carbachol-contracted taenia coli, a tissue possessing P1- (A2) and P2Y-purinoceptors and on the guinea-pig vas deferens which possesses P2X-purinoceptors. 2. In the vas deferens, where ATP (1 microM-1 mM) produced concentration-dependent contractions, ADP-ribose was without effect at concentrations up to 1 mM. 3. In the taenia coli, ADP-ribose (0.1 microM-1 mM) produced concentration-dependent relaxations with a potency similar to that of adenosine, but less than that of ATP. The pD2 values for ADP-ribose, adenosine and ATP were 4.5 +/- 0.07 (27), 4.4 +/- 0.10 (9) and 5.5 +/- 0.14 (21), respectively. The time-course of the relaxations elicited by ADP-ribose was found to be significantly longer than that for ATP and significantly shorter than that for adenosine. 4. The P1-purinoceptor antagonist, 8-Phenyltheophylline (5 microM), produced parallel rightward shifts in the concentration-response curves of the relaxations of the taenia coli elicited by ADP-ribose and adenosine but not ATP. 5. Dipyridamole (0.3 microM), a purine nucleoside uptake inhibitor, potentiated the responses to adenosine and ADP-ribose in the taenia coli. These potentiations were sensitive to 8-Phenyltheophylline (5 microM). 6. Reactive blue 2, a P2Y-purinoceptor antagonist, antagonized the inhibitory responses of ADP-ribose and ATP in the taenia coli, without significantly altering the inhibitory responses of either adenosine or noradrenaline.(ABSTRACT TRUNCATED AT 250 WORDS)
V L Saville - One of the best experts on this subject based on the ideXlab platform.
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comparison of the potency of 8 Phenyltheophylline as an antagonist at a1 and a2 adenosine receptors in atria and aorta from the guinea pig
Journal of Pharmacy and Pharmacology, 2011Co-Authors: M G Collis, D B Palmer, V L SavilleAbstract:The potency of 8−Phenyltheophylline as an antagonist at A, adenosine receptors in guinea-pig atria and at A2 adenosine receptors in the guinea-pig aorta has been investigated. 8-Phenyltheophylfine was an apparently competitive antagonist of the negative chronotropic effect of adenosine, 2-chloroadenosine, L- N6 -phenyl-isopropyl adenosine (L-PIA) and 5′- N-ethylcarboxamide adenosine (NECA) on atria and of the relaxant effect of adenosine, 2−chloroadenosine and NECA on the aorta. The pA2 values for 8−Phenyltheophylline ranged from 6.4 to 6.6 and were not significantly different, irrespective of the agonist or tissue used. These results indicate that 8−Phenyltheophylline is a relatively potent antagonist at adenosine receptors but does not exhibit selectivity for either of the putative sub-types in isolated tissues.