Fatty acid composition of phospholipids, triglycerides and cholesterol in serum of castrated and estradiol treated rats

We have studied the levels of phospholipids, triglycerides, cholesterol est ers, and their fatty acid composition in serum for normal, castrated and es tradiol treated rats. The sex hormones did not greatly affect the levels of the various lipid fractions which did not undergo great significant variat ions, under the different treatments. More evident variations occurred. in the percent composition of fatty acid and in the content of the various sat urated (SAT), unsaturated (UNSAT), essential (EFA) and non essential fatty acids (NEFA). We studied the most important ratios: EFA/NEFA; UNS/SAT; 16:0 /16:1; 18:0/18:1, 18:2/18:3; 18:2/20:4. 16:0/16:1; 18:0/18:1 represent the Delta(9) desaturase, one specific for palmitic, the other for stearic acid. 18:2/18:3 ratio is an index of the Delta(6) desaturase activity: 18:2/20:4 ratio of Delta(5) desaturase-elongase. Most changes were evident in trigly cerides. We observed a different behaviour of the UNS/SAT and EFA/NEFA rati os in phospholipids and cholesterol esters, which may reflect either an eff ect of the sex hormones on the exchange of fatty acids between the same lip id fractions, or a redistribution of lipids among different tissues. Great variations were observed of the ratios 16:0/16:1; 18:0/18:1; 18:2/18:3; 18: 2/20:4, which are ascribed a different effect of the sex hormones of Delta( 9), Delta(6), Delta(5) desaturases.