Endothelial characteristics of glomerular capillaries in normal, mercuric chloride-induced, and gentamicin-induced acute renal failure in the rat.

A reduction in glomerular capillary endothelial pore size and density has been reported in several models of acute renal failure. It has been suggested that these changes underlie the decrease in glomerular filtration rate and altered glomerular capillary hemodynamics measured in various experimental models of acute renal failure. We have thoroughly quantitated the surface characteristics of glomerular capillaries in control rats and in rats with either mercuric chloride-induced acute renal failure (2 mg/kg body wt) evaluated at 6 and 24 h after administration of the nephrotoxin or with gentamicin (G)1-induced acute renal failure evaluated after 8-9 d of 40 mg/kg body wt twice a day. Despite reductions in glomerular filtration rate in the experimental groups, no significant differences were observed between control (C) and any experimental group with respect to percent areas occupied by fenestrated endothelium (C = 53.6 +/- 2.7%; 6 h HgCl2 = 50.9 +/- 1.9%; 24 h HgCl2 = 53.9 +/- 5.7%; G = 56.7 +/- 2.4%), by cytoplasmic ridges (C = 31.2 +/- 1.5%; 6 h HgCl2 = 29.8 +/- 1.9%; 24 h HgCl2 = 30.6 +/- 3.1%; G = 26.5 +/- 1.5%), nonfenestrated endothelium (C = 15.5 +/- 4.0%; 6 h HgCl2 = 19.3 +/- 2.0%; 24 h HgCl2 = 15.6 +/- 4.3%; G = 16.9 +/- 2.3%), in the individual pore area expressed in square nanometers (C = 1,494 +/- 75; 6 h HgCl2 = 1,326 +/- 48; 24 h HgCl2 = 1,559 +/- 130; G = 1,340 +/- 101), or in the percentage of total pore area within fenestrated areas that were measured (C = 12.8 +/- 0.8%; 6 h HgCl2 = 11.2 +/- 0.7%; 24 h HgCl2 = 10.9 +/- 0.8%; G = 10.9 +/- 0.7%). These results provide quantitative data on the normal glomerular capillary endothelial surface characteristics and suggest that reductions of glomerular filtration rate in acute renal failure are not always associated with alterations in glomerular endothelial capillaries.