THE ANTI-PRESSOR ACTION OF RENAL EXTRACTS AND THEIR CAPACITY TO REDUCE THE BLOOD PRESSURE OF HYPERTENSIVE RATS

Abstract

Renal extracts were prepared which had no significant effects on the blood pressure when administered parenterally or orally to normal rats. The animals so treated exhibited a well-marked diminution in their pressor response to renin when compared to control animals which did not have preliminary treatment with the pressor-free renal extract. The agent responsible for this effect, which has in itself no direct action on blood pressure, is designated as the "renal anti-pressor substance." The renal anti-pressor substance inhibits not only the response to renin but also that of ephedrin and possibly reduces also the pressor effect of pitressin. Normal pregnant rats are less sensitive to renin than non-pregnant controls. Hypertensive rats display a pronounced spontaneous decline in blood pressure during the last few days of pregnancy, the blood pressure gradually returning after delivery to the previous level. These observations suggest that the fetus elaborates an anti-pressor substance. Extracts containing the renal anti-pressor substance cause declines in the blood pressure of hypertensive rats when administered either parenterally or orally. Similar treatment does not alter the blood pressure of normal rats,.