Abstract
We have examined the relationship between plasma renin activity and renal perfusion pressure by determining the stimulus-response curve of the renal baroreceptor in conscious, uninephrectomized dogs, and the modulation induced by catecholamines and varying salt intake. Renal perfusion pressure was controlled by step-wise inflation of a constricting cuff previously implanted around the renal artery. The stimulus-response curve of the renal baroreceptor may be divided into two ranges: a relatively flat portion close to normal pressure (100 mmHg), and a much steeper section below a “threshold” pressure of 75–80 mmHg. Epinephrine (I.V. or I.R.) produced a parallel shift of the curve to the right, i.e., a smaller drop in pressure was needed to reach “threshold”. Changing the diet from normal salt intake (80 meq/ day) to a low salt intake (10 meq/day) increased the gain of the stimulus-response curve. Thus, the same elevated PRA may be reached either by a shift of the curve to the right, or by increase in gain.