Temperature Dependency of Protein Synthesis in Isolated Hepatocytes of Antarctic Fish

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Abstract
Hepatocytes were prepared from livers of Trematomus hansoni and T. bernacchii by cannulation of the hepatic veins and collagenase perfusion at 5 C. Cells in suspension incorporated at a rate of about 15% of that observed for liver in vivo. Initial rates increased with temperature ( ) up to 20 C; however, activity declined over several hours. Longer-term survival was obtained for cells plated in modified Waymouth's medium on collagen-coated dishes. Protein synthesis ranged as high as 2 mg protein/g cells per day at 0 C, or 50% of in vivo levels. Rates increased with temperature ( ) up to an optimum of 7 C, then declined. Secretion of labeled protein by the plated cells followed a sigmoidal time course with kinetic constants similar to those determined for plasma protein secretion by liver in vivo. Protein synthesis by cells from gravid donors averaged 50% greater than those from immature females. The fraction secreted ranged from 43% for immature donors to 76% for gravid fish. Vitellogenin was identified as the major product of hepatocytes from gravid fish. The results indicate that the plated cells in stationary culture provide a good model for the behavior of the liver protein synthetic system in vivo. The role of protein synthesis in relation to the unusually narrow temperature tolerance of Antarctic fishes is discussed.