Abnormal pressure natriuresis. A cause or a consequence of hypertension?

Abstract

In all forms of chronic hypertension, the renal-pressure natriuresis mechanism is abnormal because sodium excretion is the same as in normotension despite the increased blood pressure. However, the importance of this resetting of pressure natriuresis as a cause of hypertension is controversial. Theoretically, a resetting of pressure natriuresis could necessitate increased blood pressure to maintain sodium balance or it could occur secondarily to hypertension. Recent studies indicate that, in several models of experimental hypertension (including angiotensin II, aldosterone, adrenocorticotrophic hormone, and norepinephrine hypertension), a primary shift of renal-pressure natriuresis necessitates increased arterial pressure to maintain sodium and water balance. In genetic animal models of hypertension, there also appears to be a resetting of pressure natriuresis before the development of hypertension. Likewise, essential hypertensive patients exhibit abnormal pressure natriuresis, although the precise cause of this defect is not clear. It is likely that multiple renal defects contribute to resetting of pressure natriuresis in essential hypertensive patients. With long-standing hypertension, pathological changes that occur secondary to hypertension must also be considered. By analyzing the characteristics of pressure natriuresis in hypertensive patients and by comparing these curves to those observed in various forms of experimental hypertension of known origin, it is possible to gain insight into the etiology of this disease. (Hypertension 1990;15:547-559)

Logical Issues With the Pressure Natriuresis Theory of Chronic Hypertension

“…4,5 Thus, in chronic studies of pressure natriuresis in intact hypertensive and normotensive subjects, the variable that distinguishes subjects with abnormal pressure natriuresis from normal control subjects (those with normal pressure natriuresis) is actually the level of BP, not the level of sodium excretion (because in these studies, everyone is in sodium balance and the subjects with abnormal pressure natriuresis are excreting the same amount of sodium as the normal subjects). 4,5 Note Figure 1. Examples of "chronic renal function curves" plotted on the "pressure analysis diagram. "…”

“…Hall et al 5 also state that "in all forms of chronic hypertension, the renalpressure natriuresis mechanism is abnormal because sodium excretion is the same as in normotension despite increased blood pressure" (italics added by current authors to both statements).…”

“…1 What is the meaning of statements such as "pressure natriuresis is impaired (abnormal) in all forms of chronic hypertension"? 1 To understand the meaning of this kind of statement, we substitute the operational definition of abnormal pressure natriuresis used in chronic studies of pressure natriuresis 4,5 for the phrase "pressure natriuresis is abnormal" in the statement.…”

“…1,4,5 Because "abnormal pressure natriuresis" is operationally defined as the maintenance of sodium balance in someone with increased BP, the pressure natriuresis theory of chronic hypertension holds that it is the maintenance of sodium balance that causes an initial increase in BP to become sustained. Stated in this fashion, the theory does not simply say the same thing twice in different words; it is not a proposition that is true simply based on the definition of terms used in the proposition.…”

“…9,13,14,28 These observations add to growing concerns 15,27,[31][32][33][34][35][36][37] about the pressure natriuresis theory of chronic hypertension. Accordingly, we anticipate that this theory, advanced through the pioneering efforts of Arthur Guyton and others, 4,5,13,[38][39][40][41][42] will eventually be replaced by testable theories about the abnormalities that initiate hypertension and cause it to be sustained.…”