Novel regulatory actions of 1α,25-dihydroxyvitamin D₃ on the metabolism of polyphosphoinositides in murine epidermal keratinocytes

The in vitro incubation of murine keratinocytes in the presence of 1α,25-dihydroxyvitamin D₃ enhanced the rapid hydrolysis of the prelabeled keratinocyte polyphosphoinositides (polyPtdIns) when compared to untreated cells. The rapid hydrolysis of the polyPtdIns and the release of the inositol phosphosphates (particularly InsP₃ and InsP₂) precede the onset of differentiation of these cells. These data therefore suggest that 1α,25-dihydroxyvitamin D₃ functions in vitro to initiate the rapid generation of InsP₃ from cellular polyPtdIns; this in turn may mobilize intracellular Ca²⁺, thus providing the signal which program the murine keratinocytes from a proliferating mode into a differentiating mode.