Phospholipid metabolism in calcium-regulated differentiation in cultured murine keratinocytes.

The present findings associate phospholipid alteration, particularly the turnover of phosphatidylinositol, in Ca2+ induced differentiation of keratinocytes. These conclusions are based on the hydrolysis of 14C-AA from prelabeled PI and the accumulation 14C-DG and 14C-PA after cells are switched from low to normal concentrations of extracellular Ca2+. This novel finding implies that the biological changes which accompany keratinocyte differentiation after switch from low to normal extracellular medium may be due at least in part to increased accumulation of PA and DG which are major deacylation and reacylation products of phosphatidylinositol. A second interesting finding in these studies is the marked transformation of 14C-AA into lipoxygenase products by proliferating keratinocytes cultured in low Ca2+ medium when compared to differentiating cells cultured in normal Ca2+. The significance of decreased generation of lipoxygenase products in epidermal differentiation deserve further exploration.