Adenylate cyclase activity in human liver membranes and its inhibition by adenosine and adenine nucleotides

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Abstract
The production of adenosine 3′,5'-monophosphate (cyclic AMP) in a membrane preparation from human liver homogenate has been studied. Cyclic AMP production was enhanced by glucagon, guanylyl 5'-imidodiphosphate (GMP-PNP), or fluoride, or combinations of these. Adenosine, adenosine monophosphate (AMP) and adenosine diphosphate (ADP) at a concentration of 10−3 mol/1 antagonized the effects of all stimulants. These data suggest that inhibitory effects are exercised at the catalytic moiety of the adenylate cyclase system, or at the transducer function between hormone receptor and catalytic unit. In contrast, adenosine at a concentration of 10−5 mol/1 antagonized glucagon- but not fluoride-stimulated adenylate cyclase activity.