STRUCTURAL ALTERATIONS OF RESISTANCE VESSELS OF SPONTANEOUSLY HYPERTENSIVE RATS AND PROTECTIVE EFFECTS OF CAPTOPRIL

Objective. To observe the structural alterations of resistance vessels in spontaneously hypertensive rats (SHRs) and to evaluate the effects of captopril on them. Methods. 15-week-old male SHRs were treated wit h oral captopril (100 mg/kg/day) for 12 weeks. Age- and sex-matched SH Rs and Wistar-Kyoto rats (WKY) were fed under the same conditions with out captopril administration for the same duration. All rats were kill ed at the age of 27 weeks. The structural parameters included media wi dth, lumen diameter, media-lumen ratio, vascular collagen area (VCA) a nd vascular collagen density (VCD). The media width, lumen diameter an d media-lumen ratio were measured in hhematoxylin and eosin staining s ections under a direct light microscope and VCA and VCD in picrosirius red st aining sections under a polarizing light microscope. All the v alues were processed with a computer image analyzer. Results. There we re thicker media width, smaller lumen diameter, higher media-lumen rat io and larger VCA in untreated SHRs than in WKY. Captopril inhibited m edia thickening, with lumen diameter decreasing, media-lumen ratio inc reasing and VCA enlarging. There was no significant difference in VCD among the three groups. Conclusions. Adverse structural alterations oc cur in resistance vessels of SHRs and captopril may prevent their prog ression.