Evidence that diazoxide promotes calcium influx in mouse keratinocyte cultures by membrane hyperpolarization.
We have used fura-2/AM to investigate the effect of diazoxide on the cytosolic calcium concentration (Cai) in primary mouse keratinocyte cultures. Treatment of keratinocytes with 100 microM diazoxide induced a transient peak in Cai, followed by a sustained elevation. Depletion of medium calcium by addition of EGTA abolished the diazoxide-induced Cai response, indicating that the agent promoted calcium influx without release of calcium from intracellular stores. The diazoxide-induced rise in Cai was inhibited both by addition of 60 mM KCl to the assay buffer and by preincubation with glibenclamide, a specific K+ channel blocker. In addition, studies with the membrane potential-sensitive fluorescent probe bis-oxonol demonstrated that diazoxide hyperpolarized keratinocyte membranes. These findings suggest that keratinocytes possess K+ channels, and that the previously reported proliferation effects of K+ channel openers such as diazoxide on keratinocytes may result from hyperpolarization-induced elevation of Cai.
Xiong
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Preclinical Dermatology Research, Hoffmann-La Roche, Nutley, N.J., USA.
Harmon
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CS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003981:Diazoxide / Q000494:pharmacology*; D015603:Keratinocytes / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects*; D051379:Mice; D015221:Potassium Channels / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
D015221:Potassium Channels; D014665:Vasodilator Agents; D011189:Potassium Chloride; D003981:Diazoxide; D002118:Calcium