Deacylation of ceramide, triacylglycerol and phospholipids in guinea pig epidermal cells.
The epidermal cells obtained by mild trypsinization of guinea pig skin were first labeled with [3H]palmitate. Interestingly, free ceramide was one of the major radioactive products. The radioactivity of ceramide was located exclusively in the N-acyl moiety, and palmitate was incorporated as such, without detectable chain modification. Sphingomyelin and glucosylceramide were not significantly labeled in spite of the active synthesis of ceramide. In order to investigate the action of lipolytic enzymes, the labeled cells were chased in a tracer-free medium. Bovine serum albumin (or fetal calf serum) and ionophore A23187 markedly stimulated the deacylation of lipids. The effects of the two stimulators were, however, distinctly different from each other. Bovine serum albumin (or fetal calf serum) caused principally the deacylation of triacylglycerol and ceramide, with little effect on that of phospholipids. In contrast, the effect of the ionophore was confined to phospholipid deacylation. In the presence of the ionophore, phosphatidylcholine and phosphatidylethanolamine were degraded to a similar extent. Palmitate was cleaved from both C-1 and C-2 positions of phosphatidylcholine. The results suggest that the lipolytic systems of the epidermal cells can respond to extracellular stimuli, and that the action of triacylglycerol lipase and ceramidase is controlled differently from that of phospholipases.
D000215:Acylation; D000818:Animals; D002518:Ceramides / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D004817:Epidermis / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D010168:Palmitates / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*
D002518:Ceramides; D010168:Palmitates; D010743:Phospholipids; D014280:Triglycerides