Heat stress protein-associated cytoprotection of inner medullary collecting duct cells from rat kidney.

Although heat stress proteins (HSPs) mediate thermotolerance, the cellular targets of thermal injury and mechanisms of acquired cytoprotection are unknown. To describe the metabolic effects of hyperthermia and the potential mechanisms of thermotolerance, the following were measured in inner medullary collecting duct cells after a 43 degrees C and/or a 50 degrees C thermal insult: 1) state III mitochondrial respiration (SIII MR), 2) glycolytic rate, 3) lactate dehydrogenase activity, 4) membrane permeability, and 5) HSP 72 content. Compared with controls incubated at 37 degrees C, cells heated to 50 degrees C showed a 30 and 50% reduction in glycolysis and SIII MR, respectively. After heating to 50 degrees C, the cell membrane remained intact and immunoreactive HSP 72 was not detected. In contrast, heating to 43 degrees C induced accumulation of HSP 72 and transiently increased both SIII MR and glycolysis. In addition, prior exposure to 43 degrees C completely prevented the fall in SIII MR and glycolysis anticipated with a subsequent 50 degrees C insult. Cytoprotection gradually diminished over several days and correlated with the disappearance of HSP 72. Preservation of oxidative and anaerobic metabolism associated with HSPs may be important in developing resistance to thermal injury.