THE PROHYPERTENSIVE AND ANTIHYPERTENSIVE ACTIONS OF THE KIDNEY *

THE role of the kidney in experimental renal hypertension—and prob-ably also in human renal hypertension—is twofold. On the one hand, it has a prohypertensive action mediated by the release into the blood of a pressor substance, renin, which, by acting on a serum a-globulin, produces "angiotensin, " an octapeptide with potent vasoconstrictor and pressor actions. On the other hand, the normal kidney tissue exerts some kind of anti-hypertensive action the exact nature of which is still unknown. This dual and contrariwise role is not unique in the organism. For instance, the adrenal cortex secretes hormones which may have opposite actions on inflammation in certain experimental conditions, leading Selye x to classify them as prophlogistic and antiphlogistic. If a similar situation existed for the kidney, one could hypothesize a substance which, unlike renin, serves to maintain the normal blood pressure. Such is Grollman's hypothesis.2 But the situation may be more complex, the appearance of hypertension, and perhaps also the liberation of renin by the kidney, being determined by the relation between certain demands imposed by the organism upon the kidney and its capacity to respond to them, a situation which has greater similarity to the relation between ACTH and the adrenals, or thyrotropin and the thyroid gland. THE PROHYPERTENSIVE ACTION OF THE KIDNEY Let us first consider the prohypertensive action of the kidney. In 1934 Goldblatt and his collaborators8 published a method for th