Hypertrophy of actin bundles in tubular cells in acute renal failure.

Small bundles of actin filaments are normally present in the basal part of proximal and distal renal tubular cells and are attached to the basal cell membrane. Their functional significance is unknown, but by contracting they may have a function as a modulator of the intratubular pressure. Increased thickness and number of such actin bundles have been thought to occur in various pathologic conditions, including acute renal failure (ARF), but no quantitative data have been provided. In 19 cases of ARF of the ischemic type ("acute tubular necrosis"), the volume of these bundles was determined by morphometry and expressed per unit area underlying basement membrane (BM). It was found that in ARF there is a significant twofold to fourfold increase in actin bundles in proximal and distal tubular cells compared with findings in nine controls.