Leydig cell tumor1

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 [ l-"Clarachidonate showed that the label was lost more rapidly from cholesteryl esters of HCGtreated cells than from control cells during (the 12-hour) incubation. Moreover, less [ l-"C]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.-Albert, D. H., M. Ascoli, D. Puett, and J. G. Coniglio. Lipid composition and gonadotropin-mediated lipid metabolism of the M5480 murine Leydig cell tumor. J. La+ Res. 1980. 21: 862-867. Supplementary key words human choriogonadotropin . cholesteryl ester hydrolase . phospholids . cholesteryl esters It is well established that Leydig cells respond to luteinizing hormone and human choriogonadotropin (HCG), via increased androgen production (1). However, the mechanism of action of the glycoprotein hormones has not been established. Of particular interest is the possible role that lipids may play in the steroidogenic process, not only as direct precursors to steroids (e.g., cholesterol), but also as major constituents of membranes, the biogenesis of which may be important to steroid secretion (2). Evidence has accumulated indicating that the metabolism of cholesteryl esters is under hormonal control in the adrenal (3), corpus luteum (4), and testis (5 ) . It has also been demonstrated that gonadotropins stimulate phospholipid biosynthesis in the testis (6,7); however, it is not clear if this response is due to the germinal cells or to the nongerminal cells (i.e., Sertoli and Leydig cells). In an attempt to define the lipid composition of Leydig cells and to clarify the role of lipid metabolism in the steroidogenic response of these cells to gonadotropins, an investigation of a mouse Leydig cell tumor M5480 was undertaken. Previous biochemical studies have demonstrated that the tumor and variants are ideally suited for detailed mechanism studies (811). The morphology of the tumor has been reported (12), and the tumors provide sufficient Leydig cells free of germinal cells for quantitative analysis. In the present investigation the effects of gonadotropin stimulation on the composition and metabolism of lipids and on cholesteryl ester hydrolase activity were determined. MATERIALS AND METHODS Hormones and supplies HCG was purified as previously described (13). Sodium [ 1-l4C]acetate, [ l-14C]arachidonic acid, and cholesteryl [ l-14C]linoleate were purchased from Amersham Searle (Arlington Heights, IL). Medium 199 and RPMI-1640 were obtained from the Grand Abbreviation: HCG, human choriogonadotropin. Portions of this work were presented at the FASEB Meeting, Present address: Department of Medicine, New York University Present address: Department of Medicine, Vanderbilt University, Recipient of a Research Career Development Award(AM00055). Atlantic City, April, 1978. Federation P70C. 37: 381. School of Medicine, New York, New York 10016. Nashville, T N 37232. 862 Journal of Lipid Research Volume 2 1, 1980 by gest, on N ovem er 6, 2017 w w w .j.org D ow nladed fom TABLE 1 . Lipid composition of Leydig cell tumors before and after prolonged HCG administration TABLE 2. Phospholipid composition of Leydig cell tumors before and after prolonged HCG administration Treatment" Treatment" Class Control (n = 4) HCG-Treated (n = 3) Class Control (n = 5) HCG-Treated (n = 3) Phospholipids 13.7 (2.8) 26.3 (6.6)* Cholesterol 1.8 (1.0) 2.2 (1.0) Cholesteryl esters 0.9 (0.7) 1.4 (0.6) Triacylglycerols 15.0 (4.4) 18.6 (6.1) The data are in pmoYg and standard deviations are given in parentheses. Animals were injected with 4 pg HCG daily for 3 days and the tumors were analyzed 2 hr after the last injection. Significantly different from control (P < 0.05). Island Biological Company (Grand Island, NY). All other supplies were obtained as described pre-