ANGIOTENSIN-CONVERTING ENZYME-INHIBITION IN THE POSTNATAL RAT RESULTSIN DECREASED CELL-PROLIFERATION IN THE RENAL OUTER MEDULLA

1. Chronic angiotensin converting enzyme (ACE) inhibition or AT(1) ant agonism during postnatal development in the rat has been shown to caus e renal tubular and vascular damage, particularly in the outer medulla . 2. The effects of ACE inhibition were investigated at a stage of dev elopment before the renal outer medulla is fully established. 3. Sprag ue-Dawley rat pups were given daily i.p. injections of either enalapri l or saline from days 3-10, At day 11, kidneys were perfusion-fixed fo r either electron microscopy or immunocytochemistry, Sections were inc ubated in proliferating cell nuclear antigen (PCNA) antisera and the a vidin-biotin immunoperoxidase method was used to detect an immunoreact ive product, indicative of proliferating cells. 4. Following enalapril treatment, the normal structural arrangement of the outer medulla was disrupted compared with controls, Cell proliferation (PCNA-positive c ells) in the medullary rays was reduced in enalapril-treated kidneys c ompared with control kidneys. 5. Thus, angiotensin II appears to be es sential for normal tubular and vascular growth in postnatal renal deve lopment in the rat.