Mode of action of choline. III. Metabolism of nonessential fatty acids in choline-deficient rats
To investigate the increase in ratio of C16 to C18 nonessential fatty acids in hepatic triglycerides of choline-deficient rats, two groups of rats fed, respectively, a choline-deficient and a choline-supplemented diet for 3–4 days were injected either with 1-14C-acetate intraperitoneally or with a mixture of 9,10-3H-palmitate and 18-14C-stearate intravenously. The choline-deficient and choline-supplemented rats were killed 3 h after labelled acetate injection. Further groups of choline-deficient and choline-supplemented rats were killed at intervals of 1 min to 6 h after injection with labelled palmitate and stearate. Extracts of lipids from livers and sera were analyzed by gas–liquid and thin-layer chromatography. In the choline-deficient rats injected with 1-14C-acetate the ratio of C16 to C18 labelled fatty acids incorporated into hepatic and serum triglycerides was increased and the ratio of those incorporated into hepatic and serum phospholipids was decreased. The ratio of monounsaturated fatty acids to saturated fatty acids incorporated into the triglycerides and phospholipids of liver and serum of the choline-deficient rats was decreased compared to that of the choline-supplemented rats. Similar differences between the two groups of rats were evident in the hepatic lipids of animals injected with 3H-palmitate and 14C-stearate. The early alteration of the ratios of hepatic nonessential fatty acids suggests that the initial change is a decreased desaturation of fatty acids.