Reversibility of arterial and venous changes in renal hypertensive rats.

The effect of reversal of hypertension on vascular function and composition was investigated in renal-hypertensive rats. The study comprised three groups of rats: 1) 21 male Sprague-Dawley rats with one-kidney, one clip Goldblatt hypertension of 9 weeks' duration; 2) 20 rats with one-kidney, one clip hypertension that underwent removal of renal artery clip (were "unclipped") at 6 weeks of hypertension, 3 weeks prior to the study; and 3) sham-operated normotensive control rats. Venous pressure-volume and arterial pressure-flow relationships were measured at maximal vasodilation (sodium nitroprusside and papaverine) in the denervated, pump-perfused vascular beds of the hindquarters of rats. Anatomically defined segments of the aorta and of the vena cava were removed from rats for water, sodium, and potassium analysis. Hypertension was completely reversed in the "unclipped" rats. Compared to values obtained in normotensive control rats, the water concentration of the aorta and of the vena cava, the potassium concentration of the aorta, and the sodium concentration of the vena cava were increased (p less than 0.05) in rats with one-kidney, one clip hypertension. These changes were reversed in the "unclipped" rats. In contrast, the shift of the venous pressure-volume and of the arterial pressure-flow curves toward the pressure axis at maximal vasodilation in hypertensive rats (p less than 0.02) persisted following reversal of hypertension in the "unclipped" rats (p less than 0.05). In chronic, one-kidney renovascular hypertension, the contribution of vascular wall "water-logging" to increased structural arterial resistance and decreased structural venous capacity appears to be minor.