REACTIVITY OF RENAL AND SYSTEMIC CIRCULATIONS TO VASOCONSTRICTOR AGENTS IN NORMOTENSIVE AND HYPERTENSIVE SUBJECTS*

Abstract

Observations were made on the effect of l-norepinephrine and epinephrine on the reactivity of renal arterioles in 16 normotensive subjects and 16 patients with essential hypertension. Hypertensive patients were selected in the early stages of essential hypertension as judged by minimal retinal, cardiac abnormalities and absence of proteinuria. After a suitable control period, 1-norepinephrine or epinephrine was administered at successively increasing rates ranging between 2.5 and 10.0 [mu]g/minute. Reactivity to the vasoconstrictor agents was examined by determination of systemic blood pressure and renal hemodynamics. These observations were made both during a period of normal dietary salt intake and during a period of salt restriction. Renal and systemic arteriolar vasoconstrictor reactivity was found equal in normal and hypertensive subjects as evidenced by equal relative increases in both renal resistance and systemic blood pressure in response to the administration of 1-norepinephrine and epinephrine. This observation is contrary to the thesis that essential hypertension is related to increased vascular sensitivity to circulating norepinephrine. Restricted sodium intake failed to decrease renal arteriolar vasoconstrictor reactivity to 1-norepinephrine and epinephrine in either normotensive or hypertensive subjects.