Current drug therapy of essential hypertension in relation to some of the non-renal factors which participate in the maintenance of blood pressure.

So much has been said and written about the kidney as an etiological factor in essential hypertension, almost as a unique cause, that it would be of value to review some other aspects of this disorder. Data on the possible significance of some non-renal mechanisms which function in essential hypertension in relation to the treatment of this condition by the drugs in current use would cover certain features, information on which is rather disseminated in medical scientific literature. This data is particularly important because of the emphasis often given to the results of certain types of therapy interpreted as indicating the existence of a specific etiological factor in essential hypertension controlled by this therapy. It would seem to me that for discussion this theme falls naturally into three parts: firstly, and, very briefly, the mechanism that controls the normal blood pressure; then, secondly, those features we have chosen of the haemodynamic and other changes produced by certain possible nonrenal aetiological factors which can cause hypertension; and, thirdly and finally, the comparable haemodynamic and other related changes induced by drugs used in current therapy. It is, of course, exceedingly difficult to avoid bringing the kidney into the discussion, but in the context of this review. the kidney will not be discussed in its role as the primary factor in the causation of hypertension. . Essential hypertension, for the purpose of this article, consists of a raised blood pressure with no other recognized disease to which this may be attributed. The blood pressure is considered to be raised when it is at a level (for any specific age,