The role of the renal medulla in blood pressure control.

It is well established that the renal medulla exerts a potent endocrine-like antihypertensive action. The purpose of this paper is to summarize the data that define the extent to which the renomedullary antihypertensive action is involved in blood pressure regulation. It appears that in animals kept under physiological conditions, the renal medulla is not necessary for the maintenance of normotension, since its destruction does not usually result in hypertension. However, in animals exposed to hypertensive stimuli, the presence of renomedullary tissue appears to be the key factor in resisting the increase in blood pressure. Evidence is presented to show that inherited or acquired deficiency of renomedullary antihypertensive function may contribute to the development of various forms of hypertension. It is suggested that inherited differences in the antihypertensive capacity of the renal medulla may account for differing sensitivities of various strains of animals to hypertensive stimuli. Finally, data are presented to show that renomedullary deficiency induced by a decrease in renal perfusion pressure, which could be a consequence of hypertensive damage to renal vessels, may contribute to the increase in blood pressure in various forms of hypertension.