Effects of ethanol in vitro on the beta adrenergic receptor-coupled adenylate cyclase system.
The effects of ethanol on the beta adrenergic receptor-coupled adenylate cyclase system were examined in vitro using membranes prepared from S49 lymphoma cells. Ethanol caused a dose-dependent increase in adenylate cyclase activity in membranes prepared from wild-type cells when the activity was measured in the presence of GTP. Activity measured in the presence of isoproterenol was also increased by ethanol, but the fold-stimulation by isoproterenol was lower in the presence of ethanol. Ethanol also shifted the dose-response curve for stimulation of the enzyme by isoproterenol to the right. This shift was due to a decrease in the affinity of the beta adrenergic receptor for isoproterenol. A decrease in the affinity of the receptor for the antagonists [125I]iodopindolol and propranolol was also observed, but the magnitude of this effect was less than that seen with the agonist isoproterenol. The density of binding sites for [125I]iodopindolol was not affected by ethanol. Dose-response curves for NaF and guanosine-5'-O-(3-thiotriphosphate), both of which stimulate adenylate cyclase activity through an effect on the stimulatory guanine nucleotide-binding protein (Gs), were shifted to the left by the addition of ethanol. In membranes prepared from the CYC- variant of S49 cells, which lacks the alpha subunit of Gs, guanosine-5'-O-(3-thiotriphosphate) inhibited forskolin-stimulated adenylate cyclase activity. The inhibition by guanosine-5'-O-(3-thiotriphosphate) was not affected by ethanol. In membranes prepared from both wild-type and CYC- S49 cells, ethanol inhibited forskolin-stimulated adenylate cyclase activity. Whereas the inhibition of this activity by GTP was greatly attenuated in membranes prepared from CYC- S49 cells which had been pretreated with pertussis toxin, the inhibition by ethanol was not affected by pretreatment with pertussis toxin.(ABSTRACT TRUNCATED AT 250 WORDS)
Bode
D C
DC
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia.
Molinoff
P B
PB
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008223:Lymphoma / Q000201:enzymology; D008970:Molecular Weight; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology
D011943:Receptors, Adrenergic, beta; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000431:Ethanol; D006160:Guanosine Triphosphate; D011433:Propranolol; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D007545:Isoproterenol