McMartin L, Summers R J
Department of Pharmacology, University of Melbourne, Parkville, Australia.
Life Sci. 1995;57(11):1039-49. doi: 10.1016/0024-3205(95)02049-o.
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.
给豚鼠输注β-肾上腺素能受体激动剂异丙肾上腺素（400微克/千克/小时，持续7天），并使用[3H]福斯高林检测心脏腺苷酸环化酶。心脏中存在两类[3H]福斯高林结合位点，与载体（1 mM盐酸）相比，异丙肾上腺素输注后其亲和力（解离常数KD分别为2 nM和280 nM）和密度（最大结合量Bmax分别为9和900 fmol/毫克蛋白）未发生变化。[3H]福斯高林结合的放射自显影定位也未改变。10 mM氟化钠（NaF）和10 μM 5'-鸟苷酰亚胺二磷酸（Gpp(NH)p）这两种G蛋白激活剂分别使载体处理动物心脏中的[3H]福斯高林结合增加100%和80%。然而，在异丙肾上腺素处理的动物中，NaF刺激的结合未改变，而Gpp(NH)p刺激的结合减少了35%，这可能表明Gi的影响增加。
