Glomerular number and size following chronic angiotensin II blockade in the postnatal rat

Chronic angiotensin-converting enzyme (ACE) inhibition with enalapril or angiotensin II (Ang II) receptor antagonism with either losartan (specific for Ang II type-1 receptor, AT₁) or PD 123319 (specific for the Ang II type-2 receptor, AT₂) were effected between postnatal days 3 and 21 in the rat. Following quantitative analysis of the kidneys using recently developed unbiased stereological techniques we found that none of the treatments resulted in changes in glomerular number or size. This implies that inhibition of Ang II activity had no effect on postnatal nephron induction or glomerular development. However, following both chronic ACE inhibition and AT₁ antagonism, abnormalities of tubules and their associated vessels were evident throughout the kidney and were accompanied by an increased proportion of interstitium. The structural abnormalities were most prominent in the outer medulla and were consistent with interruption of descent of the loops of Henle and vasa rectae. In contrast, no renal morphological abnormalities were observed following chronic AT₂ antagonism.