KERATINOCYTE K-INDUCED DIFFERENTIATION( CHANNELS MEDIATE CA2+)

K+ channel activation has been associated with growth or differentiati on in many cells. We have previously identified a 70-pS K+ channel tha t was found only in differentiated involucrin-positive cells. In this study we examined the role of K+ channels in Ca2+-induced keratinocyte differentiation. Consistent with our previous report, we found that a K+ conductance developed only in cells cultured in high extracellular Ca2+, Addition of charybdotoxin or verapamil blocked these K+ channel s and inhibited Ca2+-induced differentiation, as assessed by cornified envelope formation or transglutaminase activity. These results sugges t that K+ channel activation is necessary for Ca2+-induced differentia tion. Finally, we used I-125-labeled charybdotoxin to demonstrate the presence of K+ channels in intact human and mouse epidermis, hair foll icles, and eccrine glands, indicating that these channels are found in keratinocytes both in vitro and in vivo. Thus K+ channels may moderat e Ca2+ influx in more differentiated keratinocytes and may play a cent ral role in keratinocyte differentiation.