Hemodynamic effects of enalapril on neonatal chronic partial ureteral obstruction.

To evaluate the role of angiotensin II (ANG II) in renal vasoconstriction due to ipsilateral CPUO, guinea pigs were subjected to incomplete left ureteral stenosis within the first 48 hr of life, and were given enalapril from the 14th day of life until study at 23 +/- 3 days or 8 weeks of age. Renal blood flow (RBF) was measured using radioactive microspheres, and glomerular filtration rate (GFR) was derived from inulin extraction. The number of perfused glomeruli per kidney was determined following in vivo India ink perfusion. Enalapril treatment resulted in an 83% rise in RBF of the obstructed kidney, from 2.58 +/- 0.26 to 4.73 +/- 0.48 ml/min (P less than 0.001), which was associated with a 26% increase in number of perfused glomeruli (P less than 0.01). Mean GFR of the hydronephrotic kidney increased from 0.13 +/- 0.02 to 0.37 +/- 0.10 ml/min (P less than 0.05). Enalapril had no effect on intraureteral pressure of the obstructed left kidney after 7 to 13 days of administration, and did not affect renal mass or ureteral diameter after 6 weeks of treatment. It is concluded that hemodynamic consequences of CPUO in the neonate may be attenuated by ANG converting enzyme inhibition. The primary effect of enalapril is most likely inhibition of intrarenal ANG II formation.