Reversal of two-kidney one clip renovascular hypertension in the rat.

Abstract
Attempted correction of 2-kidney, 1 clip Goldblatt hypertension in the rat was performed by 3 techniques: removal of the constricting clip, removal of the ischemic kidney and converting enzyme blockade by oral captopril. Since duration of hypertension is said to be a critical factor, groups of rats were studied after short term (< 6 wk from clipping) and chronic (> 4 mo.) hypertension. Blood pressure, Na balance and plasma renin concentration (PRC) were followed before and after these correcting procedures. In a control group of animals, removal of a loose renal artery clip did not influence blood pressure and only caused trivial postoperative retention of Na. Unclipping normalized blood pressure in both short-term and chronic hypertension. After a major postoperative fall, blood pressure returned to somewhat elevated levels after nephrectomy in animals with chronic (but not short-term) hypertension. Na balance became markedly positive with the fall in blood pressure of operated hypertensive animals and was significantly correlated with the fall in blood pressure in these 4 groups at 7 days. Captopril produced a fall in blood pressure at 24 h, with a positive Na balance, but the relationship between blood pressure fall and Na balance did not reach statistical significance. The PRC was elevated in all hypertensive groups, but individual values overlapped with values from normal rats and nonhypertensive rats with a loose renal artery clip. The PRC fell to normal or subnormal values after either operative procedure and stabilized for at least 2 mo. independently of whether blood pressure fell or not. Na retention and renin hypersecretion do not maintain blood pressure in this model. The rapidity of the blood pressure fall is not consistent with a role for vascular hypertrophy. The greater efficacy of unclipping suggests that the revascularized kidney after this procedure exerts a vasodepressor function independent of Na excretion or the renin-angiotensin system.