Morphometric analysis of effects of angiotensin II on glomerular structure in rats.

Micropuncture and morphometric studies related the effects of angiotensin II (ANG II) on glomerular function and structure. Compared with control animals, rats receiving an intrarenal infusion of ANG II at 40 ng.kg-1.min-1 exhibited a marked reduction in the glomerular ultrafiltration coefficient (Kf) (0.84 +/- 0.13 vs. 1.43 +/- 0.05 microliters.s-1.mmHg-1, ANG II vs. control), which caused a decrease in glomerular filtration rate (GFR) (1.04 +/- 0.11 vs. 1.27 +/- 0.11 ml/min) despite an increase in glomerular transcapillary hydraulic pressure difference (46 +/- 1 vs. 40 +/- 1 mmHg). Morphometric studies showed that these hemodynamic changes were not associated with any reduction in glomerular volume (1.27 +/- 0.05 vs. 1.31 +/- 0.07 x 10(6) microns3, ANG II vs. control), glomerular capillary volume (4.25 +/- 0.36 vs. 4.41 +/- 0.33 x 10(5) microns3), or glomerular peripheral capillary surface area (2.24 +/- 0.11 vs. 2.29 +/- 0.30 x 10(5) microns2). Higher-power electron 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 filtration slit length overlying the peripheral capillary wall (7.0 +/- 0.6 vs. 6.6 +/- 0.5 x 10(5) microns), or reduce the average width of individual filtration slits (45 +/- 2 vs. 43 +/- 2 nm). ANG II infusion thus caused a 40% reduction in the value of Kf without causing detectable changes in epithelial cell or filtration slit structure.