The glomerular filtration barrier in the spontaneously hypertensive rat.

To determine whether the differences in the physiological characteristics of SHR and WKY kidneys might be related to differences in renal structure, we studied the kidneys of SHR and WKY rats utilizing scanning and transmission electron microscopy and latex perfusion of the glomerular vasculature. Scanning and transmission electron microscopy revealed a smaller diameter in the glomerular endothelial fenestrae of SHR compared to that in WKY rats even prior to the development of differences in blood pressure. With age, the density and diameter of SHR endothelial fenestrae progressively decreased, which was not true in WKY rats. Latex casts of glomerular vasculature showed the frequent presence of afferent arteriolar constriction in 12-week-old SHR. Thus, the filtration barrier of the SHR is abnormal. THe pathogenesis of hypertension in the SHR is complex and probably multifactorial; however, renal structural changes may contribute to the development and maintenance of hypertension. The afferent arteriolar constrictions may be the structural basis for the increased vascular resistance described in the SHR.