出版社：American Society for Biochemistry and Molecular Biology
摘要：The effects of human choriogonadotropin (HCG) stimulation on lipid composition in the murine Leydig cell tumor M5480 grown subcutaneously were determined. The main lipids of the Leydig cell tumor were found to be largely triacylglycerols and phospholipids. Daily in vivo administration of human choriogonadotropin to tumor-bearing mice for 3 days increased the phospholipid content and altered the phospholipid composition of the tumors. There was no demonstrable change in the levels of triacylglycerols, cholesterol, and cholesteryl esters. HCG had no major effect on the fatty acid patterns of the major lipid fractions with the exception of cholesteryl esters, which had a decreased amount of arachidonic acid following HCG-treatment. Results of in vitro incubations of tumor cells prelabeled with [1-14C]arachidonate showed that the label was lost more rapidly from cholesteryl esters of HCG-treated cells than from control cells during (the 12-hour) incubation. Moreover, less [1-14C]acetate was incorporated into the cholesteryl ester fraction of hormone-treated cells than in control cells. HCG stimulated the activity of cholesteryl ester hydrolase in dispersed cells within 3 hours. These results demonstrate that an acute effect of HCG on tumor Leydig cell metabolism is to increase the metabolism of cholesteryl esters, probably by stimulating cholesteryl ester hydrolase activity. The long term effect is an accumulation of phospholipids which may be utilized for membrane synthesis.
