Chronic Captopril Infusion in Two-kidney, One Clip Rats with Normal Plasma Renin Concentration

Immediately after clipping, plasma renin and angiotensin II concentrations are raised in the two-kidney, one clip rat. Plasma renin and angiotensin II fall to relatively low levels between two and five weeks after operation, while blood pressure continues to rise. An experiment was carried out to determine whether complete suppression of angiotensin II during this two- to five-week period would have any effect on the development of hypertension. Captopril infused chronically (2 mg/kg/h) for up to 20 days completely prevented the rise in mean blood pressure [110.8 +/- 17.9 at day 0 compared to 88.3 +/- 8.4 (s.d.) mmHg at day 20] seen in an equivalent control group infused with dextrose (109.2 +/- 11.6 at day 0 compared to 131.7 +/- 23.6 mmHg at day 20). Preinfusion values for plasma renin and angiotensin II concentration were within the upper half of the range found for sham-operated normal rats. These findings would suggest that while the plasma levels of angiotensin II are low in relation to those seen immediately after clipping, they are still raised in comparison with normal sham-operated rats; this may contribute to the development of hypertension by a slow chronic, rather than an acute, effect.