Altered Peripheral Responsiveness to βBt-Adrenergic Stimulation in Experimental RenaL Hypertension

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Abstract
Hypertension, induced in male rats by encapsulation of both kidneys with latex envelopes, is associated with a reduction in maximal responsiveness to β-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 β-adrenergic agonist. At doses of isoproterenol in excess of 6μg/kg body weight, s.c., the dipsogenic response of rats with renal hypertension was significantly (p > 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 20μg/kg body weight, s.c., plasma renin activity was elevated significantly (p > 0.01) in the normotensive, but only in the lowest dose in the renal hypertensive group. These results suggest that maximal responsiveness to β-adrenergic stimulation is reduced in the renal hypertensive rat; however, the mechanism(s) responsible for the reduced β-adrenergic responsiveness remains speculative.