Exercise training changes the gating properties of large-conductance Ca 2+-activated K + channels in rat thoracic aorta smooth muscle cells

Abstract

Large-conductance Ca 2+-activated K + (BK Ca) channels play a critical role in regulating the cellular excitability in response to change in blood flow. It has been demonstrated that vascular BK Ca channel currents in both humans and rats are increased after exercise training. This up-regulation of the BK Ca channel activity in arterial myocytes may represent a cellular compensatory mechanism of limiting vascular reactivity to exercise training. However, the underlying mechanisms are not fully understood. In the present study, we examined the single channel activities and kinetics of the BK Ca channels in rat thoracic aorta smooth muscle cells. We showed that exercise training significantly increased the open probability ( Po), decreased the mean closed time and increased the mean open time, and the sensitivity to Ca 2+ and voltage without altering the unitary conductance and the K + selectivity. Our results suggest a novel mechanism by which exercise training increases the K + currents by changing the BK Ca channel activities and kinetics.