Antihypertensive and hypertensive effects of the kidney. Elucidated by treatment with medullary transplants and with blockade either of the reninangiotensin-system or of the prostaglandin biosynthesis.

After subcutaneous isotransplantation of renal medulla either from normal donors or from the ischaemic kidney of renal two-kidney hypertensive rats, the blood pressure of the renal two-kidney hypertensive recipients was lowered-but not to normal levels. After i.v. injection of the converting enzyme inhibitor SQ 20,881, the blood pressure was further decreased to, or close to, normal blood pressure. A complete normalization of the blood pressure was obtained by the combined treatment with medullary transplants and infusions of the angiotensin II inhibitor Saralasin. The difference between the effects of these two blockers was probably caused by differences in the doses used. Administration of indomethacin, an inhibitor of the prostaglandin biosynthesis, to renal two-kidney hypertensive rats with or without renomedullary transplants failed to provoke a rise in blood pressure. This indicates that the anti-hypertensive activity of renomedullary transplants is not due to the group of prostaglandins, the synthesis of which is inhibited by indomethacin, and furthermore that these prostaglandins are not of importance to the blood pressure level in renal two-kidney hypertensive rats.