Pathogenesis of malignant hypertension: experimental evidence from the renal hypertensive rat

In rats with unilateral renal artery stenosis, the malignant phase of hypertension is characterized by: systolic blood pressure above 180-190 mm Hg; sodium and water loss; polyuria and polydipsia; markedly activated renin-angiotensin-aldosterone system; impairment of renal function and malignant nephrosclerosis in the contralateral kidney; some rats exhibit signs of cerebral hemorrhage, heart failure, acute renal failure, and some rats die. After such a phase of malignant hypertension, a period of remission may occur, which is followed by another malignant phase, etc. When malignant hypertensive rats are offered, in addition to water, saline as drinking fluid, they compulsively drink the saline, BP falls transiently, and all signs of malignant hypertension nearly or completely disappear. These observations indicate that, at a critically high BP level, it is salt and water loss which, by activating the renin-angiotensin system, trigger the vicious circle of malignant renal hypertension in rats.