Effects of cilazapril on the retinal vessels in spontaneously hypertensiverats: Corrosion cast and scanning electron microscopic study

The effects of the long-term oral angiotensin-converting enzyme in hi biter , cilazapril, on retinal circulation in stroke-prone spontaneously hyperten sive (SHR-SP) rats were assessed by scanning electron microscopy (SEM), cor rosion casts and transmission electron microscopy (TEM). Two groups of 20 m ale SHR-SP rats were compared. One group was treated with 10 mg/kg/day of c ilazapril from 4 to 40 weeks of age, and the other group received no treatm ent. A third group of male Wistar-Kyoto (WKY) rats served as age-matched co ntrols. At regular intervals the rats were weighed, and their systolic bloo d pressure was measured. Cilazapril normalized systolic arterial pressure t o 121 +/- 2.7 mm Hg (SD) in the treated SHR-SP rats. There was no significa nt difference in body weight between the two groups of SHR-SP. In the 40-we ek-old SHRSP rats without treatment corrosion cast and SEM revealed hyperte nsive retinal vascular changes. In the 40-week-old SHR-SP rats treated with cilazapril, these changes were markedly decreased to the level seen in WKY rats. The differences in caliber of retinal capillaries between the treate d SHR-SP and untreated SHR-SP rats were statistically significant (p<.0001) . TEM in the cilazapril-treated SHR-SP rats revealed intact basement membra nes (0.29+/-0.057 mu m) of the endothelial cells and pericytes, but in the untreated SHR-SP rats the basement membrane was thickened (0.51 +/- 0.123 m u m) (p<.0001) and the pericytes damaged. Our results show that the long-te rm administration of cilazapril decreased systolic arterial pressure to a n early normal level and prevented hypertensive retinal vascular changes, pro bably by improving endothelial function. The effects of cilazapril on the r etinal vasculature are described for the first time. SEM of corrosion casts is a valuable technique for showing the effects of some drugs on the vascu lature easily, precisely and three-dimensionally. (C) 1998 Elsevier Science Inc.