1-ALKYL-2,3-DIACYLGLYCEROL SYNTHESIS IN PRIMARY CULTURE CELLS OF GUINEA-PIG HARDERIAN-GLAND

Using a primary culture system of guinea pig Harderian gland cells, we investigated the metabolism of a unique lipid: 1-alkyl-2,3-diacylglyc erol containing methyl-branched fatty acids. The cells were obtained b y collagenase digestion, and cells with lipid-droplets were collected by two-step centrifugation. We cultured these cells, and examined thei r lipid and fatty acid compositions. The de novo synthesis of lipids i n these cells was studied as to the incorporation of [1(2)-C-14] aceta te and [U-C-14] glucose. The major lipid proved to be 1-alkyl-2,3-diac ylglycerol, as in tissue, and it contained a large amount of methylbra nched fatty acids specific to this gland. The incorporation of [C-14] acetate and [C-14] glucose into 1-alkyl-2,3-diacylglycerol in the cult ured cells amounted to 79.7 and 88.2% of the total incorporation into the lipid fraction, respectively. The incorporation of [C-14] acetate into fatty acids in the cultured cells was detected for the chain leng ths of C14 to C25. The activities of glycerol-3-phosphate dehydrogenas e in the cultured cells and Harderian gland were lower than that in ad ipose tissue. These results confirm that cultured cells reflect the li pid metabolism originating in the Harderian gland and show that this c ulture system can serve as one part of the armamentarium for further s tudy of this unique lipid metabolism.