Fatty‐acyl coenzyme A pool in liver of rainbow trout (Salmo gairdneri): Effects of temperature acclimation

The size and composition of the hepatic acyl‐CoA pool were determined in quickly frozen liver tissue of rainbow trout (Salmo gairdneri) acclimated to 5° and 20°C. Concentrations of 14:0‐, 16:1‐, 18:3‐, 20:2‐, 20:3‐, and 24:1‐CoA were significantly higher while proportions of 18:0‐, 18:1‐, 20:1‐, and 20:4‐CoA were significantly lower in warm‐ than cold‐acclimated trout. In spite of these differences, neither the size (although 28% larger in warm‐ than cold‐acclimated trout), total content of unsaturated acyl‐CoAs, average chain length, nor the degree of unsaturation of the acyl‐CoA pool was significantly influenced by acclimation temperature. Arachidonic acid (20:4n6) was the only polyunsaturated fatty acid present in significantly higher quantities in the acyl‐CoA pool of cold‐ than warm‐acclimated trout. Levels of n‐3 acids were similar in both acclimation groups, while proportions of n‐9 and n‐6 acids increased and decreased, respectively, with cold acclimation. It is concluded: 1) that the composition of the acyl‐CoA pool is unlikely to influence significantly the acyl chain composition of membrane lipids and 2) that the temperature dependence of substrate preference for the enzymes of phospholipid biosynthesis and turnover is likely to play a major role in determining which molecular species of phospholipid will accrue as environmental temperature changes.