The pathophysiology of renin release in renovascular hypertension.

Renovascular hypertension (RVH) results from occlusion of blood flow to either kidney, which stimulates renin release. Increased renin leads to a series of actions that rapidly leads to increased systemic blood pressure. Experimental renovascular hypertension is developed in animals by placement of a clip that occludes more than 50% of renal blood flow to that kidney. The major stimulus for renin release in renovascular hypertension is the severe drop in hydrostatic pressure in the afferent arteriole, the location of the juxtaglomerular renin-secreting granular cells. The pressure drop changes the degree of stretch of these cells which leads to baroreceptor-mediated renin release. The level of renin released can be modified by sympathetic nerves and to a lesser degree by the macula densa. Several hormone or vasoactive agents may augment renin released during RVH, but nearly all are secondary to changes in the pressure receptor mechanism.