Effect of angiotensin-converting enzyme inhibition on renal filtration surface area in hypertensive rats

Background. Angiotensin-converting enzyme (ACE) inhibitor treatment leads to protective effects on the cellular structure of the glomerulus and the kidney. The aim of this study was to determine whether ACE inhibition increases renal filtration surface area in the spontaneously hypertensive rat (SHR). Methods. SHR were treated with the ACE inhibitor perindopril at a high dose (3 mg/kg/day) or a low dose (0.1 mg/kg/day) during the period of hypertension development, from 7 to 14 weeks of age. Some animals were treated concomitantly with the bradykinin B-2 receptor antagonist, S16118. Tail-cuff systolic blood pressure and body weights were measured twice weekly. At termination of treatment, glomerular number and volume, length, and surface area of glomerular capillaries and renal filtration surface area were estimated using unbiased stereological techniques. Results. There were significant dose-related reductions in blood pressure with high- and low-dose perindopril treatment. Neither low- nor high-dose perindopril treatment had any effect on glomerular number or size or glomerular capillary length and surface area. Hence, there was no significant difference in total renal filtration surface area between any of the experimental groups (8721 +/- 610 mm(2) in untreated SHR and 7879 +/- 338 mm(2) and 8767 +/- 437 mm(2) in the low and high dose perindopril-treated groups, respectively). Coadministration of the bradykinin antagonist did not affect any of the glomerular parameters. Conclusions. ACE inhibition during the period of hypertension development does not lead to an enhanced glomerular capillary growth or increases in total renal filtration surface area in this model.