Tubular ultrastructure in acute renal failure: alterations of cellular surfaces (brush-border and basolateral infoldings).

Using a blind, semiquantitative technique, the degree of reduction of proximal tubular brush border (BB) and proximal and distal basolateral infoldings (BI) were measured in 25 renal biopsies from patients with acute renal failure (ARF) of ischaemic type. For comparison 12 biopsies from patients without ARF were studied, 6 were normal controls, six were from patients with minor change disease and slight glomerulonephritis. The mean scores for reduction of BB as well as proximal and distal BI were strongly increased in ARF compared to controls and the differences were highly significant. Some of the biopsies were taken during recovery and there was a significant negative correlation between the individual scores for reduction of BB and BI and simultaneous renal function. The disappearance of BB microvilli was correlated to tubular dilatation, but it could not be explained exclusively by "stretching" of the luminal surface due to dilatation. There was no correlation between reduction of BI and tubular dilatation. The data indicate a disturbance of cell membrane turnover in the active phase of ARF, possibly due to decreased synthesis, and they are consistent with a pathogenetic hypothesis implicating a decreased proximal Na+ resorption and consequently a pre-glomerular vasoconstriction.