Renal afferent arteriolar structure in the genetically hypertensive (GH) rat and the ability of losartan and enalapril to cause structural remodelling

Objective This study aimed to compare the structure of renal afferent arter ioles in the genetically hypertensive (OH) rat strain with the normotensive (N) control strain in relation to pathogenesis, and to quantify structural remodelling in OH rats after treatment with losartan and enalapril and to relate this to blood pressure (BP) and left ventricular (LV) mass. Methods OH rats were given losartan 15 mg/kg/day, enalapril 10 mg/kg/day (e nalapril 10) or 3 mg/kg/day (enalapril 3) from the age of 4 to 10 weeks. Un treated OH and N groups served as controls. Tail-cuff systolic BP was measu red weekly from 4 weeks. At the age of 10 weeks, kidneys were perfused with microspheres to identify afferent arterioles, kidney pieces were fixed, em bedded in Technovit and stained sections analysed. Lumen and media plus lum en diameters were measured; media width, media cross-sectional area (CSA) a nd media/lumen (M/L) ratio were derived. Results BP and LV mass were elevated in OH compared with N rats, and reduce d by losartan and enalapril 10 end to a lesser degree by enalapril 3. In ef ferent arterioles, lumen diameter, media width end CSA were smaller in OH t han N and M/L ratio was larger. Losartan and enalapril 10 reduced media wid th and increased lumen diameter, while enalapril 3 increased CSA (in distal arterioles) and lumen diameter. M/L ratio was reduced by losartan and enal april. Conclusion Abnormal structure of the afferent arteriole, resulting in an in creased M/L ratio, could explain abnormalities of renal blood flow end vasc ular resistance in OH and contribute to the hypertension. In OH, losartan a nd enalapril reduce BP and LV mass, cause remodelling of afferent arteriole s, and lower the M/L ratio to below N levels. J Hypertens 1998, 16:1945-195 2 (C) 1998 Lippincott Williams & Wilkins.