EFFECTS OF ESTRADIOL AND TESTOSTERONE ON INCORPORATION AND DISTRIBUTION OF [ME-14C]METHIONINE METHYL IN RAT LIVER LECITHINS

1. 1. Castrated male rats were injected for 3 weeks with testosterone propionate (2 mg/week), estradiol benzoate (100 μg/week) or sesame oil alone (0.3 ml/week). They were injected intraperitoneally with 3.3 μC of [Me-14C]methionine per 100 g body weight 1 h before they were killed. 2. 2. Liver phosphatidylethanolamines and lecithins were separated by thin-layer chromatography, and radioactivity and fatty acids were determined. In addition, lecithins were separated, according to unsaturation, into tetraenes (mainly 20:4, but contained 22:5 and 22:6 fatty acids also), triene, diene, and monoene subfractions by AgNO3-silicic acid thin-layer chromatography, and counted. 3. 3. Estradiol increased the incorporation of the methyl label into the lecithins, whereas testosterone had neither a stimulatory nor inhibitory effect. 4. 4. Estradiol increased proportions of stearic acid and polyenoic acids (> 20:4) and decreased linoleic acid in liver lecithins as compared with the other groups. 5. 5. The largest part of the methyl label in the lecithins of all groups was in the tetraene subfraction (> 65%) which also had the highest specific activity. The next largest portion was in the diene subfraction. The methyl label incorporation into the lecithin subfractions was closely associated with the amount of a given fraction in the total lecithins. 6. 6. Estradiol increased the stearic acid content and the proportion of the tetraene subfraction while decreasing the relative proportion of the diene subfraction. 7. 7. A close relation between the labeled choline of the lecithins and the content of stearic acid in a given fraction was observed for all groups-a relationship not shown by palmitic, oleic or linoleic acids. 8. 8. The results indicated that estradiol enhanced the methylation of phosphatidylethanolamine and increased the formation of lecithins containing stearic and long-chain polyene fatty acids (20:4 and higher). The relationship of the labeled choline to stearic acid and the highly unsaturated fatty acids suggested that fatty acid composition influenced the methylation of phosphatidylethanolamines. © 1968.