title: Mitochondrial alpha-glycerophosphate dehydrogenase activity in active and torpid ground squirrels, Spermophilus richardsoni.
abstract: 1. Mitochondrial alpha-glycerophosphate dehydrogenase (GPD) activity was assayed in liver homogenates from active and torpid ground squirrels. 2. Arrhenius plots of GPD activity were linear in non-hibernating animals and discontinuous in hibernators. Compared with non-hibernators, the energy of activation in hibernators was reduced between 37 and 25 degrees C, but increased between 25 and 6 degrees C. 3. A dose-response relation between GPD activity and injected thyroxine was determined in active animals. No correlation was found between enzyme activity at 37 or 6 degrees C and circulating titres of thyroid hormones, in ground squirrels sampled during the preparative and hibernating phases.
mesh_terms: D000818:Animals; D001143:Arousal; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism*; D006605:Hibernation; D008930:Mitochondria, Liver / Q000201:enzymology*; D012589:Sciuridae / Q000502:physiology*; D013816:Thermodynamics
chemical_list: D005993:Glycerolphosphate Dehydrogenase