RENAL MEDULLARY BLOOD-FLOW AND RENAL MEDULLARY ANTIHYPERTENSIVE MECHANISMS

It has long been recognised that the kidneys take part in blood pressu re control via both their exocrine and endocrine functions. An endocri ne antihypertensive function of the renal medulla has been proposed. T he renal medullary depressor substances (''medullipins''), are release d in response to increased renal perfusion pressure. It has been sugge sted that the release of ''medullipin'' is controlled via changes in r enal medullary blood flow. Recent observations also suggest that renal medullary blood flow is involved in the control of the pressure/natri uretic-diuretic action of the kidney. In this review we outline a unif ied hypothesis for blood pressure control via a combination of the pla sma volume regulating pressure-natriuresis mechanism and the powerful antihypertensive actions of the ''medullipins'' (i.e. vasodilatation, inhibition of sympathetic drive and a diuretic action). It is hypothes ised that the activity of both these systems are under control by rena l medullary blood flow.