[3H]forskolin binding to cardiac adenylate cyclase in guinea pigs chronically infused with isoproterenol.
Guinea pigs were infused with the beta-adrenoceptor agonist isoproterenol (400 micrograms/kg/hr, 7 days) and cardiac adenylate cyclase was detected using [3H]forskolin. Two populations of [3H]forskolin binding sites were present in heart, the affinities (KD 2 nM and 280 nM) and densities (Bmax 9 and 900 fmol/mg protein) of which were unchanged by isoproterenol infusion compared with vehicle (1 mM HCl). The autoradiographic localisation of [3H]forskolin binding was also unchanged. The G protein activators NaF 10 mM and 5'-guanylylimidodiphosphate (Gpp(NH)p) 10 microM increased [3H]forskolin binding in heart from vehicle-treated animals by 100% and 80% respectively. NaF-stimulated binding was unchanged in isoproterenol-treated animals, however, Gpp(NH)p-stimulated binding was reduced by 35% which may indicate an increased influence of Gi.
McMartin
L
L
Department of Pharmacology, University of Melbourne, Parkville, Australia.
Summers
R J
RJ
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D005576:Colforsin / Q000378:metabolism*; D005260:Female; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006168:Guinea Pigs; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D012969:Sodium Fluoride / Q000494:pharmacology
D005576:Colforsin; D006165:Guanylyl Imidodiphosphate; D012969:Sodium Fluoride; D000262:Adenylyl Cyclases; D007545:Isoproterenol