GLYCOLYTIC ENZYME BINDING DURING ENTRANCE TO DAILY TORPOR IN DEER MICE (PEROMYSCUS-MANICULATUS)

Associations of glycolytic enzymes with the subcellular particulate fr action of skeletal muscle and heart were examined during entrance to d aily torpor in deer mice (Peromyscus maniculatus). In skeletal muscle a significant decrease in enzyme binding occurred during torpor entran ce for phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase, with an additional significant decrease for phosp hofructokinase and pyruvate kinase during the deepest state of torpor. Reductions in enzyme binding during torpor entrance also occurred in heart; significant changes were observed in hexokinase, glyceraldehyde -3-phosphate dehydrogenase, and pyruvate kinase binding. Contrary to t he finding of additional reductions in enzyme binding seen in skeletal muscle, significant increases in enzyme binding during the deepest to rpor state were observed for hexokinase, phosphofructokinase, glyceral dehyde-3-phosphate dehydrogenase, pyruvate kinase, and lactate dehydro genase in heart. These results suggest that a decrease in the binding of glycolytic enzymes to subcellular structures in skeletal muscle and heart may be at least partially responsible for initiating the reduct ion in metabolic rate during torpor entrance. This decreased binding m ay continue to mediate the metabolic reduction in skeletal muscle thro ughout torpor; heart, however, may require the use of different molecu lar mechanisms. The increased binding in heart during the deepest stat e of torpor may represent an anticipatory response in preparation for increased activity during arousal.