CHANGES IN THE LEVELS OF GLYCEROPHOSPHOINOSITOLS DURING DIFFERENTIATION OF HEPATIC AND NEURONAL CELLS

Glycerophosphoinositols are metabolites formed by a phospholipase A(2) and lysolipase specifically acting on membrane phosphoinositol lipids . High levels of these compounds characterize epithelial cells adn fib roblasts transformed by ras and other cellular oncogenes. Here we have analyzed the glycerophosphoinositol levels in cells that are consider ed models of cell differentiation. Using rat hepatocytes at different stages of liver development we have shown that the glycerophosphoinosi tol basal levels of fetal cells were up to fourfold higher than in adu lt hepatocytes. No changes in glycerophosphoinositol were observed in regenerating rat liver, a model of differentiated cells proliferating in a synchronous manner, where only glycerophosphoinositol 4-phosphate increased by 80%. Similarly to fetal hepatocytes, a modest but signif icant increase (30%) in the levels of glycerophosphoinositols was obse rved in undifferentiated NG-108-15 cells as compared to the same cells induced to differentiate by cAMP. In a different neuronal cell line, PC12 cells, increased glycerophosphoinositol levels characterized the differentiated cells. Based on these observations we suggest that high glycerophosphoinositol levels characterize cellular phenomena associa ted with the activation of ras/mitogen-activated protein kinase pathwa ys.