Changes in phosphatidylinositol metabolism during differentiation of lens epithelial cells into lens fiber cells in the embryonic chick.

During the development and growth of the lens, lens epithelial cells differentiate to form lens fiber cells. The present study investigates phosphatidylinositol metabolism in these two lens cell populations in the 6-day-old embryonic chick in vivo, to determine whether changes in the metabolism of this phospholipid are associated with lens fiber differentiation. [32P]Orthophosphate was injected into the embryos in ovo, and the incorporation of label into phosphatidylinositol in the lens epithelia and lens fiber masses was followed for 42 h. The time course of the specific activity of the gamma-PO4 of ATP was also determined during this time period, and was shown to be approximately equal to the specific activity of CDP-diacylglycerol, the immediate precursor of phosphatidylinositol. Analysis of the data by means of a simple kinetic model yielded a value of about 2 x 10(-9) pmol/s/cell for the rate of phosphatidylinositol synthesis in the lens epithelial cells, and 6.4 x 10(-9) pmol/s/cell in the lens fiber cells; the corresponding half-lives of phosphatidylinositol were 5 h and 63 h in the epithelial cells and fiber cells, respectively. Thus, lens fiber formation in the 6-day-old embryonic chick is associated with increased synthesis and decreased turnover of phosphatidylinositol. This is the first report of changes in phosphatidylinositol metabolism associated with cell differentiation during embryonic development.