MORPHOMETRIC ANALYSIS OF EFFECTS OF ANGIOTENSIN-II ON GLOMERULAR STRUCTURE IN RATS

Micropuncture and morphometric studies related the effects of angioten sin II (ANG II) on glomerular function and structure. Compared with co ntrol animals, rats receiving an intrarenal infusion of ANG II at 40 n g.kg(-1).min(-1) exhibited a marked reduction in the glomerular ultraf iltration coefficient (K-f) (0.84 +/- 0.13 vs. 1.43 +/- 0.05 mu l.s(-1 ).mmHg(-1), ANG II vs. control), which caused a decrease in glomerular frltration rate (GFR) (1.04 +/- 0.11 vs. 1.27 +/- 0.11 ml/min) despit e an increase in glomerular transcapillary hydraulic pressure differen ce (46 +/- 1 vs. 40 +/- 1 mmHg). Morphometric studies showed that thes e hemodynamic changes were not associated with any reduction in glomer ular volume (1.27 +/- 0.05 vs. 1.31 +/- 0.07 x 10(6) mu m(2), ANG II v s. control), glomerular capillary volume (4.25 +/- 0.36 vs. 4.41 +/- 0 .33 x 10(5) mu m(3)), or glomerular peripheral capillary surface area (2.24 +/- 0.11 vs. 2.29 +/- 0.30 x 10(5) mu m(2)). Higher-power electr on micrographs showed that ANG II also did not alter mean foot process width (478 +/- 14 vs. 491 +/- 18 nm, ANG II vs. control), reduce the total frltration slit length overlying the peripheral capillary wall ( 7.0 +/- 0.6 vs. 6.6 +/- 0.5 x 10(5) mu m), or reduce the average width of individual filtration slits (45 +/- 2 vs. 43 +/- 2 nm). ANG II inf usion thus caused a 40% reduction in the value of K-f without causing detectable changes in epithelial cell or filtration slit structure.