title: Modulation of glycogen phosphorylase activity affects 5-phosphoribosyl-1-pyrophosphate availability in rat hepatocyte cultures.
abstract: The effect of modulation of the rate of glycogenolysis on the availability of 5-phosphoribosyl-1-pyrophosphate (PRPP) was investigated in rat hepatocyte cultures. Dibutyryl cyclic AMP (dbcAMP), forskolin and glucagon, activating glycogen phosphorylase through activation of protein kinase A (PKA), were found to raise PRPP availability by 44%-56%. Arg-vasopressin and phenylephrine, activating glycogen phosphorylase through the phosphoinositide cascade, did not affect PRPP availability. dbcAMP, but not phenylephrine, increased the degradation of pre labeled glycogen by 57%. Caffeine and CP-91149, inhibitors of glycogen phosphorylase, decreased PRPP availability by 33% and 43%, respectively. The finding that induction of glycogenolysis enhances, and inhibition of glycogenolysis decelerates PRPP generation suggests that glycogenolysis is a major contributor to PRPP generation in liver tissue in the basal (postabsorptive) state.
authors.affiliation: Felsenstein Medical Research Institute, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Pnina
authors.initials: P
authors.lastname: Boer
authors.forename: Oded
authors.initials: O
authors.lastname: Sperling
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000737:chemistry; D003994:Bucladesine / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology; D005576:Colforsin / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005934:Glucagon / Q000737:chemistry / Q000378:metabolism; D024981:Glycogen Phosphorylase / Q000235:genetics* / Q000378:metabolism*; D022781:Hepatocytes / Q000201:enzymology* / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D010656:Phenylephrine / Q000737:chemistry / Q000378:metabolism; D010754:Phosphoribosyl Pyrophosphate / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D000577:Amides; C110844:CP 91149; D007211:Indoles; D001127:Arginine Vasopressin; D005576:Colforsin; D010656:Phenylephrine; D002110:Caffeine; D003994:Bucladesine; D010754:Phosphoribosyl Pyrophosphate; D005934:Glucagon; D024981:Glycogen Phosphorylase; D017868:Cyclic AMP-Dependent Protein Kinases