| Abstract: | Adenylate cyclase activity in the myocardium and aorta of Grollman one-kidney renal hypertensive rats (RHR) and sham-operated control rats was compared. The experimental rats revealed significantly higher blood pressure and cardiac hypertrophy 6-8 weeks postoperation as compared to controls. Basal, guanine nucleotide-, fluoride-, and isoproterenol-stimulated adenylate cyclase activities were consistently decreased in the myocardium of RHR as compared to control rats. Similar changes were observed in aorta of RHR; however, the magnitude of difference was greater in aorta as compared to myocardium. The kinetic properties of enzyme with regard to the Ka (quantity of agonist required for half-maximal stimulation of adenylate cyclase) values for GTP, Gpp (NH)p, and GTP-gamma-S in the absence and presence of isoproterenol and the Ka values for isoproterenol in the presence of GTP, Gpp(NH)p, or GTP-gamma-S were comparable in RHR and control rats. However, Vmax of adenylate cyclase stimulation by guanine nucleotides, isoproterenol, and fluoride was reduced in RHR as compared to control rats. No differences between RHR and control rat myocardial membranes were observed in the affinity of [3H]DHA binding. However, the number of binding sites was reduced 20-25% in RHR as compared to control rats. These data would suggest that the number of receptor--cyclase complexes may be reduced in the RHR. |
