Potassium Channels in Human Umbilical Artery Cells

MILESI V; RAINGO J; REBOLLEDO A; GRASSI DE GENDE AO

JOURNAL OF THE SOCIETY FOR GYNECOLOGIC INVESTIGATION.

Elsevier

Año: 2003 vol. 10 p. 339 - 346

1071-5576

Potassium channels are expressed diffusely in the plasma membrane of different kinds of vascular smooth muscle cells, and they have been involved in the regulation of membrane potential, an important factor involved in excitation-contraction coupling. Activation of potassium channels insmooth muscle cells produces hyperpolarization and vasorelaxation,whereas their inhibition induces depolarization andcontraction. Therefore, the activity of potassium channels playsan important role in the maintenance of resting tone and in the active responses to endogenous or exogenous vasoactive substances. Concerning the functional role of large-conductanceCa2-activated K channels (BKCa) in human vessels, wepre viously reported that BKCa-carried currents were involvedin the control of resting membrane potential and vascular tone of the saphenous vein.1 KCa channels also regulate human pial artery tone2 and the contractile response to nitrovasodilators in human coronary arteries.3In the human umbilical artery (HUA), one of the vessels involved in fetoplacental circulation, the mechanisms that regulate the contractile state of smooth muscle cells are very important in order to achieve optimal gas and nutrients exchange between the fetus and the placenta. Using K channelsblockers on human umbilical artery rings, Lovren and Triggle have recently reported that nitric oxide-induced relaxation involves the activation of delayed rectifier K channels (KDR)and KCa channels.4 But to the best of our knowledge, there are no reports that study the characteristics of K channels insmooth muscle cells from these arteries with electrophysiologictechniques. In order to characterize the composition of Kcurrents in freshly enzymatically dispersed HUA smooth muscle cells, we present in this paper whole-cell currents showingthe presence of KDR and BKCa channels, and single channel data where BKCa properties are studied. We also present evidence that these channels are functional in intact tissue andare implicated in the maintenance of the resting vascular tone.