SEXUAL DIFFERENCES IN BRANCHED-CHAIN AMINO-ACID-METABOLISM INTO FATTY-ACIDS AND CHOLESTEROL IN HARDERIAN-GLAND OF GOLDEN-HAMSTER

The Harderian gland of golden hamster (Mesocricetus auratus) secretes copious lipids, most of which is 1-alkyl-2,3-diacylglycerol (ADG). We previously reported that the composition of ADG shows marked sexual di morphism [Seyama ct al. (1995) J. Biochem. 117, 661-670]. Male ADG con tains only straight chain alkyl and acyl groups, but female ADG contai ns a lot of branched chain ones too. In this study, we investigated th e metabolism of branched chain amino acids (BCAAs) and analyzed the in corporation of the metabolites into lipids in the Harderian gland. Gol den hamsters were injected intraperitoneally with [ U-C-14] BCAAs, and Harderian glands were obtained at 3, 6, 9, and 24 h after injection. Lipids were then extracted from the glands and analyzed. Thin layer ch romatography revealed that the ADG was labeled in both sexes, but the profile depended on the sex. The cholesterol fraction was labeled only in the male gland. The alkyl and acyl groups of ADG were subjected to radio-gas liquid chromatography. As for the alkyl groups, radioactivi ty was detected in straight-C16 and -C18 chains in males, while branch ed-C17 and -C19 chains were labeled in females. As for the acyl groups , straight-C14, -C15, and -C16 chains were labeled in males, while in females, branched-C17 and -C19 chains were labeled as well as a straig ht-C16 chain. These results suggest that the BCAA metabolism should be regulated as to the sex at the step of branched chain acyl-CoA degrad ation in the Harderian gland of golden hamster, which causes the sexua l dimorphism in the lipid composition in this gland.