Kryshtal D. The characteristic of potassium ionic currents of smooth muscle cell membrane of rat vas deferens

Using patch-clamp technique in configuration "perforated patch" it was shown that outward potassium current in single smooth muscle cells isolated from epididymal part of rat vas deferens consists of Ca2+-dependent potassium current (KCa) via BKCa channels and voltage-gated transient A-type current which had very fast kinetic of activation and inactivation and delayed rectifier current which showed delayed kinetics of onset and a rather slow time course of inactivation. Based on the properties of studied voltage-gated currents, concluded that delayed rectifier current plays an important role in the controlling of the resting membrane potential, while transient A-type current may take part in the regulation of the electrical excitability of rat vas deferens smooth muscle cells. It was shown the ability of selective blocker of large conductance KCa channels paxilline to evoke the depolarization of the cell membrane at potentials more positive than -45 mV in smooth muscle cells of rat vas deferens. Takinginto account these results we concluded that in the rat vas deferens smooth muscle cells Ca2+ dependent K+ channels take part in the regulation of the membrane potential during depolarization of the cell membrane. Effect of KN-93, a specific membrane-permeable inhibitor of Ca2+/calmodulin-dependent protein kinase II (CaMKII), on transient A-type potassium current was also studied. Application of 5 µM KN-93 essentially accelerated inactivation of the A-type current and significantly slowed down its recovery from inactivation. These results suggest that in smooth muscle cells of epididymal part of rat vas deferens transient A-type potassium current can be modulated by Ca2+/calmodulin-dependent protein kinase II activity.