IN-VITRO HEPATOCYTE METABOLISM OF ALANINE AND GLUCOSE AND THE RESPONSE TO INSULIN IN FED AND FASTED RAINBOW-TROUT

Rainbow trout (Oncorhynchus mykiss) fasted for 4 months had lower plas ma glucose concentration and hepatocyte glycogen content than the fed fish. Gluconeogenesis from alanine in the fasted fish was not signific antly different from that of the fed fish, whereas both alanine glycon eogenesis and oxidation increased with fasting by 400% and 300%, respe ctively. Glyconeogenesis from glucose was not significantly different with fasting, whereas glucose oxidation decreased significantly with f asting. The presence of glucose (10 mM) in the medium did not modify a lanine glyconeogenesis or gluconeogenesis in either the fed or the fas ted groups. However, glucose did increase alanine oxidation in the fed group but not in the fasted group, this response being further stimul ated in the presence of insulin. Alanine (2 mM) in the medium had no e ffect on glyconeogenesis from glucose in either fed or fasted trout he patocytes. Insulin significantly decreased glucose oxidation in the fe d fish, whereas the insulin effect on glucose oxidation in the fasted fish occurred only in the presence of alanine. The results indicate th at nutritional state affects hepatocyte responsiveness to substrate ut ilization and insulin stimulation in trout. Specifically, the hepatocy te potential for glyconeogenesis is enhanced in the fasted fish, altho ugh this increased glycogen production is not due to an increased gluc ose utilization. (C) 1995 Wiley-Liss, Inc.