Kidney structural changes in rats following inhalation exposure to C10-C11 isoparaffinic solvent

Kidney tissues from Fischer 344 rats exposed by inhalation to either 5.48, 1.83, or 0.0 g/m3 of C10-C11 isoparaffinic solvent vapor for 5, 20 and 40 days (6 h/day, 5 days/week), followed by a 4-week recovery period, were examined by light microscopy (LM) and electron microscopy (EM). At the LM level, an increased incidence of protein droplets was found in the cytoplasm of renal tubular epithelial cells of the exposed male rats relative to controls. Other renal changes observed by LM in the exposed male rats included foci of regenerative epithelium and tubular dilatation with intratubular protein occurring between the inner and outer stripe of the medulla. By EM, the protein droplets were electron dense, angular, crystalline-like structures which were surrounded by acid phosphatase positive reaction product corresponding to remnants of membrane-bound phagolysosomes. After 20 and 40 days of exposure there was focal loss of the brush border, with degeneration and sloughing of necrotic cells. Following a 4-week recovery period reversal of the exposure-related tubular changes was indicated by EM. The kidney changes observed in male rats following exposure to light hydrocarbons have not been observed in female rats or other species and may be unique to the male rat.