ACCLIMATION TO LOW-TEMPERATURE IS ASSOCIATED WITH AN INCREASE IN LONG-CHAIN ACYL-COA SYNTHETASE IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) HEART

Rainbow trout (Oncorhynchus mykiss) were acclimated to 5 and 15 degree s C. Uptake of radiolabelled palmitate by isolated cardiomyocytes was linear for at least 65 min. Myocytes from fish acclimated to 5 degrees C and tested at 5 degrees C showed higher rates of uptake than those from fish acclimated to 15 degrees C and tested at 5 degrees C. There was no significant difference in fatty acid uptake between myocytes fr om fish acclimated to 5 and 15 degrees C and tested at their respectiv e acclimation temperature. Acclimation temperature had no effect on le vels of intracellular fatty acid binding protein or carnitine palmitoy ltransferase. However, acclimation to low temperature resulted in a tw ofold enhancement in fatty acyl-CoA synthetase activity, which increas ed in a linear fashion over a 28-day period. An increase in fatty acyl -CoA synthetase, which occurs on the outer mitochondrial membrane and the endoplasmic reticulum, is possibly related to low temperature-indu ced changes in fatty acid oxidation and synthesis of complex lipids.