1. In an investigation of the prolonged pressor response to renin that develops after nephrectomy, angiotensin I dose—response curves and rat renin clearances were studied in nephrectomized rats and paired sham-nephrectomized control animals under pentobarbitone anaesthesia.
2. Both threshold and slope of the angiotensin I dose—response curves were decreased at 15–27 h after nephrectomy.
3. The ratio of renin clearance (determined during renin infusions) in the nephrectomized rat to that in the paired sham-nephrectomized control animals was 0·49 ± 0·03 (sem), P < 0·001 (n = 12 pairs).
4. Both factors contribute towards the prolongation of the blood pressure increase after intravenously administered renin in the nephrectomized animal.