Abstract
Rainbow trout (Salmo gairdneri) were acclimated to either 5 or 20°C, and then transferred to the opposite temperature, and changes in the fatty acid composition of liver microsomal membranes and the activities of the hepatic Δ9, Δ6, and Δ5 desaturases were measured at intervals of up to one month post-transfer. Inital changes (days 0–3) in fatty acid composition were: (1) an increase in the proportion of saturates and a decrease in the proportion of polyunsaturates during warm acclimation, and (2) a decrease in the proportion of saturates during cold acclimation. The activity of the Δ6 desaturase approximately doubled immediately following the changes in temperature, but alterations in Δ9 and Δ5 desaturase activities required at least 3 days to occur. The results indicate that desaturase enzymes do not play a major role in the initial adaptation of membrane fatty acid composition to changes in temperature. However, the desaturase enzymes may be involved in the later stages (3–28 days) of the acclimatory process. The proportion of monoenes was well correlated with Δ9 desaturase activity during both transfers, and appeared to be adjusted as required to offset changes in the proportion of polyunsaturates.
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