Ultrastructural Alterations of Rat Liver Subsequent to Heat Overload

Abstract : Light and electron microscopic changes were demonstrated in the livers of older (400-500g) rats which were associated with both exercise at 26C and sedentary exposure to 41.5C. Exhaustive exercise at 5C produced neither fatalities nor pathological changes in the liver that could be detected by light or electron microscopy. In contrast, exhaustive exercise at 26C was fatal for most heavy rats. Electron microscopy showed loss of endothelial cells lining the sinusoids of the liver, loss of parenchymal cell microvilli, and vacuolization of parenchymal cells. Survival for 24 hrs. after such exercise resulted in extensive centrilobular necrosis. Exposure to 41.5C, while at rest, was always fatal when the mean maximal core temperature reached 42.3 plus or minus 0.1C. Light microscopy of livers from these rats showed peracute focal centrilobular necrosis and intestinal necrosis. Electron microscopy demonstrated changes in the liver similar to those observed after exhaustive exercise at 26C. The changes observed in our experimental rats are consistent with those observed in human heatstroke.