title: The adenylate cyclase activity of isolated hepatocytes actions of glucagon and sodium fluoride.
abstract: Isolated hepatocytes converted exogenous [alpha-32P]ATP to cyclic [32P]AMP at high rates. This system was used for kinetic studies of the effects of glucagon, fluoride, free magnesium and free ATP4- on adenylate cyclase. In the absence or presence of glucagon, free Mg2+ activated adenylate cyclase by decreasing the Km for MgATP2- without changing V. Free ATP4- was not a potent inhibitor of adenylate cyclase and the only effect of glucagon was to increase V. Fluoride also increased the V of adenylate cyclase, but, in contrast to the results obtained with glucagon, the effect increased as the concentration of free Mg2+ increased. One explanation of the effect of fluoride, consistent with the idea that free Mg2+ activates adenylate cyclase and free ATP is not an inhibitor, is that fluoride increases the affinity of the enzyme for Mg2+. Weak inhibition of adenylate cyclase by ATP4- in the presence of fluoride cannot be excluded.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005459:Fluorides / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D051381:Rats; D012969:Sodium Fluoride / Q000494:pharmacology*
chemical_list: D000255:Adenosine Triphosphate; D012969:Sodium Fluoride; D005934:Glucagon; D000262:Adenylyl Cyclases; D008274:Magnesium; D005459:Fluorides