SKELETAL-MUSCLE PH DYNAMICS DURING AROUSAL FROM HIBERNATION MEASURED BY P-31 NMR-SPECTROSCOPY

The time-course of changes in skeletal muscle pH during arousal from hibernation in the Columbian ground squirrel was studied using31P NMR spectroscopy. In hibernation (Tre 7-9°C), shoulder/neck muscle pH was 7.45±0.03 and αIm was 0.60. In euthermia (Tre 37°C), muscle pH was 7.24±0.05 and αIm was 0.75. Thus the overall pH-temperature coefficient was-0.009 pH units/°C, indicating acidification of the muscle in hibernation. During the transition from hibernation to euthermia, however, the muscle shows a nonlinear pattern of pH change. In early arousal (Tsh<20-25°C, Tre<15°C) muscle pH does not change and muscle αIm increases to 0.72. In later arousal (Tsh>20-25°C, Tre>15°C) muscle pH decreases gradually toward the euthermic value and muscle αIm increases only slightly from 0.72 to 0.75. These results support the hypothesis that intracellular acidification of the muscle, present during hibernation, is reversed in early arousal. This may facilitate an increase in muscle metabolism and the contribution of maximal shivering thermogenesis to rewarming of the animal. © 1990 Springer-Verlag.