1. Successive infusions of SQ 20 881 given intra-arterially (i.a.) to the kidney at 0.4 and 0.8 μg min−1 kg−1 for 50 min each did not alter renal blood flow and renal vascular resistance in spite of 40–47% blockade of the angiotensin I (ANG I i.a.)-induced vasoconstrictor response.
2. SQ 20 881 administered intravenously (i.v., 0.5 mg/kg) after the higher intra-arterial dose did not further decrease the renal response to ANG I (i.a.), but caused an increase in renal blood flow and a decrease in renal vascular resistance.
3. These results indicate that SQ 20 881 has limited efficacy in blocking the renal response to ANG I (i.a.). Under the conditions of these experiments, the renal vasodilator response to SQ 20 881 appears to be due to inhibition of extrarenal rather than intrarenal converting enzyme.