Minoxidil sulfotransferase, a marker of human keratinocyte differentiation

The sulfation of minoxidil is catalyzed by a sulfotransferase activity in a number of tissues including skin. To investigate further the nature of the minoxidil sulfotransferase activity in epithelial tissue and to compare this activity to that of cholesterol sulfotransferase, which has already been shown to be induced during the differentiation of epithelial cells, we cultured normal human epidermal keratinocytes in a keratinocyte growth medium for 4 d, after which the media were replaced with either the same growth media or media with increasing Ca++ concentrations. Cholesterol sulfotransferase, minoxidil sulfotransferase, and transglutaminase were determined during the differentiation of the cells in the three media. Time-activity curves that suggested two different sulfotransferase activities were induced during the differentiation process. U-77581, a competitive inhibitor of minoxidil sulfotransferase activity, inhibited the sulfation of minoxidil sulfotransferase activity in the keratinocyte homogenates, but it did not inhibit the sulfation of cholesterol. These data indicate that at least two sulfotransferase activities are induced during the differentiation of epithelial keratinocytes and minoxidil sulfotransferase is an early marker of that differentiation.