Angiotensin converting enzyme inhibition and autoregulation of glomerular filtration

The present study examines the influence of two angiotensin converting enzyme (ACE) inhibitors, perindopril and captopril, on renal plasma flow and on autoregulation of glomerular filtration in anaesthetized rats during reduction of renal perfusion pressure to 100, 90 and 80 mmHg. Groups 1 and 3 had a normal sodium intake (4 mmol/kg per day), while groups 2 and 4 were sodium depleted (0.5 mmol/kg per day) for 10 days. Renal perfusion pressure was measured before and after ACE inhibition in all groups. Groups 1 and 2 were given perindopril (0.3 mg/kg) and groups 3 and 4 were given captopril (3.0 mg/kg) intravenously. When renal perfusion pressure was reduced in group 1 following ACE inhibition with perindopril, the glomerular filtration rate remained unaltered. In group 3, captopril abolished autoregulation of the glomerular filtration rate, which decreased from 1.01 +/- 0.03 to 0.60 +/- 0.03 ml/min. Similarly, reduction in renal perfusion pressure was associated with an unaltered glomerular filtration rate in group 2, but in group 4 the glomerular filtration rate fell more significantly, from 0.89 +/- 0.06 to to 0.19 +/- 0.3 ml/min. Renal plasma flow decreased significantly in groups 1 and 3 during the renal perfusion pressure changes, both before and during ACE inhibition, but in groups 3 and 4 it remained relatively stable. These results indicate that ACE inhibition with captopril alters the normal autoregulation of the glomerular filtration rate, presumably by blocking the angiotensin II (Ang II) efferent arteriole vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)