Evidence of injury by heat in mammalian tissues

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Abstract
Some possible criteria of injury by heat were investigated using slices of rat liver, cerebral cortex, and renal cortex heated in vitro. The following were measured at approximately 1-C intervals between 40 and 47.5 C, and in each case the results were compared with controls incubated for the same time at 38 C: Qo2, the increase of ammonia, urea, cholesterol, and acid phosphatase in the suspension medium, and the leakage of Rb86 from tissues labeled with this isotope in vivo. In general, deviation from the control at a given temperature increased with time. For a given tissue, several or all of these deviated from the control at about the same temperature. For cerebral cortex this was about 43 C and for liver about 45 C. The most sensitive indicator of injury appeared to be the accumulation of ammonia in the medium, and this deviated from controls at 40 C for renal cortex and 42 C for liver and cerebral cortex. Thus, there is evidence for several biochemical changes produced by heating in vitro to temperatures at or below those at which irreversible changes occur in vivo.