title: Stimulation of rat and cat heart adenylate cyclase by triiodothyronine in the presence of 5'-guanylylimidodiphosphate.
abstract: Adenylate cyclase activity in particulate preparations from the myocardium of rats and cats was unaffected by 3,3',5-triiodo-L-thyronine (L-T3) added in the absence of, or together with, 5-guanylylimidodiphosphate (Gpp(NH)p), a potent activator of the enzyme. Preincubation of the heart particles with Gpp(NH)p made the cyclase sensitive to L-T3 which then caused, in concentrations of 10(-8) M and higher, additional increases in enzyme activity up to about 50 per cent above the Gpp(NH)p-stimulated level. Similar effects after (GPP(NH)p treatment were produced by low concentrations of 3,3',5'-triiodo-L-thyronine (reverse T3) and 3,3',5-triiodo-D-thyronine, whereas diiodo-tyrosine, 3,5-diiodo-L-thyronine, and 3'-isopropyl-3,5-diiodo-L-thyronine were without significant effect. The stimulatory action of L-T3 on cardiac adenylate cyclase pretreated with Gpp(NH)p may help to explain some of the acute effects of thyroid hormones on the heart that have been reported in the literature.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006321:Heart / Q000187:drug effects*; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010710:Phosphates / Q000494:pharmacology; D051381:Rats; D013329:Structure-Activity Relationship; D014284:Triiodothyronine / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D010710:Phosphates; D014284:Triiodothyronine; D000262:Adenylyl Cyclases