Altered peripheral responsiveness to beta-adrenergic stimulation in experimental renal hypertension

Hypertension, induced in male rats by encapsulation of both kidneys with latex envelopes, is associated with a reduction in maximal responsiveness to beta-adrenergic stimulation. Responsiveness was assessed by measurement of both water intake and plasma renin activity following acute subcutaneous administration of graded doses of isoproterenol, a beta-adrenergic agonist. At doses of isoproterenol in excess of 6 micrograms/kg body weight, s.c., the dipsogenic response of rats with renal hypertension was significantly (p less than 0.05) less than that of normotensive controls. Basal, unstimulated plasma renin activities were similar in both the normotensive and renal hypertensive groups. However, following administration of isoproterenol at doses of 5, 10, or 20 micrograms/kg body weight, s.c., plasma renin activity was elevated significantly (p less than 0.01) in the normotensive, but only in the lowest dose in the renal hypertensive group. These results suggest that maximal responsiveness to beta-adrenergic stimulation is reduced in the renal hypertensive rat; however, the mechanism(s) responsible for the reduced beta-adrenergic responsiveness remains speculative.