Effect of Hypothermia on the Cellular Respiration of Ventricular Tissue

¹ From the Arctic Aeromedical Laboratory, APO 731, Seattle, Washington

The respiration of ventricular slices and homogenates in the presence of various substrates was studied in control normothermic and experimental hypothermic rats. The Q_oo2 of the slices prepared from rats cooled to a rectal temperature of 15°C was significantly higher than that of control normothermic animals. No difference in the rate of oxidation of ventricular homogenates was observed between the two groups except when no substrate was used or when pyruvate was added as the test substrate. In the absence of substrate, there was a tendency toward higher rates in the hypothermic group, whereas addition of pyruvate caused a significant depression in the oxygen consumption of this group. Addition of malate to the pyruvate containing medium produced a marked increase in respiratory rate. The data obtained indicate that hypothermia does not have any adverse irreversible effect on the function of the tricarboxylic acid cycle and its associated enzyme systems. The results do suggest a possible alteration in membrane permeability, an accumulation of reduced intracellular intermediates, or both as a result of the hypothermic episode.