Eccentric contractions affect muscle membrane phospholipid fatty acid composition in rats

This study investigated if prior eccentric contractions, and thus mechanica l strain and muscle damage, exert an effect on the muscle membrane phosphol ipid fatty acid composition in rats, and whether a possible effect could be attenuated by dietary supplements. Twenty-three rats were randomised to th ree groups who received chow with added fish oil (n = 8), vitamin C (n = 8) or no supplement (n = 7). After 3 weeks of feeding, calf muscles on one si de were stimulated electrically during anaesthesia causing eccentric contra ctions. Two days later the white gastrocnemius, a part of the stimulated ca lf muscle, was excised from both legs. In the muscles stimulated to contrac t eccentrically compared to the control muscles, the proportion of arachido nic acid, C20:4,n-6 (17.7 +/- 0.6; 16.4 +/- 0.4% of total fatty acids, resp ectively) and docosapentanoeic acid, C22:5,n-3 (2.9 +/- 0.1 and 2.7 +/- 0.1 % of total fatty acids, respectively) was uniformly higher across groups ( P < 0.02) with no differences between diet groups. The proportion of long c hain polyunsaturates was also significantly higher in the eccentrically con tracted (39.9 +/- 0.6% of total fatty acids) compared to the control leg (3 8.2 +/- 0.6 % of total fatty acids; P < 0.01). In contrast no differences w ere observed in the fatty acid composition of the triacylglycerols stored w ithin the muscle. Thus one severe bout of eccentric contractions modulates the fatty acid composition of the muscle membrane phospholipids when compar ed to a control leg, and supplemental intake of fish off or vitamin C did n ot attenuate this effect.