Protein metabolism in hepatic tissue of hibernating and arousing ground squirrels

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Abstract
Protein metabolism in hepatic tissue of hibernating, arousing, and normothermic ground squirrels, Citellus tridecemlineatus, was assessed by 3 methods: measurement of alanine-U-C14 utilization by liver slices; incorporation of methionine (methyl-Cl4) into protein by microsomal preparations from liver; measurement of arginase activity in liver homogenates. Measurements were made at 6 and 37 C. In comparison to hepatic tissue of normothermic animals: protein synthesis from methionine and lipogenesis from alanine were markedly lowered in hepatic tissue of hibernating and arousing animals when measured at 37 C, whereas no change was observed at 6 C; incorporation of alanine into hepatic glycogen was increased in hibernating animals at 6 and 37 C. In comparison to hepatic tissue of hibernating animals: oxidation of alanine to CO2 was increased in hepatic tissue of arousing and normothermic animals at 6 and 37 C; arginase activity was increased in hepatic tissue of arousing animals at 6 and 37 C and in normothermic animals at 37 C. These data suggested an increased protein catabolism during arousal.