Hypoxic pulmonary vasoconstriction (HPVC) is mediated, in part, via membrane depolarization and inhibition of K+ channels. We recently observed that the naturally occurring
steroid dehydroepiandrosterone (
DHEA) reversed and prevented HPVC in isolated perfused and ventilated ferret lungs. In the current study, we investigated the effects of
DHEA on the major K+ channels of chronically hypoxic human pulmonary smooth-muscle cells (HPSMC). K+ channels were recorded by using the patch-clamp technique in whole-cell and single-channel configurations. Single-channel recordings were performed in inside-out and outside-out excised patches, and in intact HPSMC in cell-attached configuration. Using whole-cell current recording, chronic
hypoxia decreased the high-amplitude, high-noise, and
charybdotoxin-sensitive Ca2+-dependent K+ channels (KCa).
DHEA reversed the effect of chronic
hypoxia on KCa, but had no effect on the low-amplitude, low-noise, and 4-aminopyridine-sensitive delayed rectifying K+ channels. In the cell-attached configuration, chronic
hypoxia caused a decrease in KCa sensitivity to membrane potential (Em).
DHEA reversed the effect of
hypoxia on KCa sensitivity to Em and caused a mean of 40-mV left shift in voltage-dependent activation of KCa.
DHEA increased KCa activation from both sides of membrane patches of hypoxic HPSMC via a cyclic
adenosine monophosphate- and cyclic
guanosine monophosphate-independent pathway. We concluded that
DHEA is a novel KCa opener of the human pulmonary vasculature.