The Kidney in Blood Pressure Regulation

Despite extensive animal and clinical experimentation, the mechanisms responsible for the normal regulation of arterial pressure and development of essential or primary hypertension remain unclear. One basic concept was championed by Guyton and other authors [1–4]: the long-term regulation of arterial pressure is intimately linked to the ability of the kidneys to excrete sufficient sodium chloride to maintain normal sodium balance, extracellular fluid volume, and blood volume at normotensive arterial pressures. Therefore, it is not surprising that renal disease is the most common cause of secondary hypertension. Furthermore, derangements in renal function from subtle to overt are probably involved in the pathogenesis of most if not all cases of essential hypertension [5]. Evidence of generalized microvascular disease may be causative of both hypertension and progressive renal insufficiency [5,6]. The interactions are complex because the kidneys are a major target for the detrimental consequences of uncontrolled hypertension. When hypertension is left untreated, positive feedback interactions may occur that lead progressively to greater hypertension and additional renal injury. These interactions culminate in malignant hypertension, stroke, other sequelae, and death [7]. In normal persons, an increased intake of sodium chloride leads to appropriate adjustments in the activity of various humoral, neural, and paracrine mechanisms. These mechanisms alter systemic and renal hemodynamics and increase sodium excretion without increasing arterial pressure [3,8]. Regardless of the initiating factor, decreases in sodium excretory capability in the face of normal or increased sodium intake lead to chronic increases in extracellular fluid volume and blood volume. These increases can result in hypertension. When the derangements also include increased levels of humoral or neural factors that directly cause vascular smooth muscle constriction, these effects increase peripheral vascular resistance or decrease vascular capacitance. Under these conditions the effects of subtle increases in blood volume are compounded because of increases in the blood volume relative to L. Gabriel Navar L. Lee Hamm