ACCUMULATION OF 1-O-ALKYL-2,3-DIACYLGLYCEROLS IN CULTURED RAT KERATINOCYTES

The present study was undertaken to identify the chemical structure of neutral lipid accumulated in cultured rat keratinocytes and to addres s their metabolism. Neutral lipid of similar mobility with alkyldiacyl glycerol was isolated from cultured rat keratinocytes by thin layer ch romatography. The long-chain diols derived from the neutral lipids wer e identified as 1-alkylglycerol based on the mass spectra of their nic otinylidene derivatives. Thus these neutral lipids were identified as 1-o-alkyl-2,3-diacylglycerols (ADAG). Addition of rat serum elevated t he level of ADAG with increasing trend of linoleic acid concentration in this fraction. [C-14]Acetate added to the confluent plates was inco rporated into alkyl- and acyl-chains of ADAG with incubation in 24 h, and remained un-metabolized up to 72 h. This, however, is not the case for the label incorporation into phospholipid and triacylglycerol. Ra dioactivities of these two lipid fractions appeared to reach the maxim um in 24 h, and thereafter decreased to 72 h with a similar decay curv e. Incorporation of [C-14]acetate into phospholipid and ADAG was signi ficantly depressed, and that into triacylglycerol and foe cholesterol was increased by the supplementation of the medium with rat serum. In concomitance with the accumulation of ADAG, the concentration of ethan olamine-plasmalogen increased in the cultured keratinocytes. The resul ts of the present study first showed the elevated level of ether lipid synthesis in the proliferating primary culture of rat keratinocytes.