Properties of the high-conductance Ca2+-activated K+ (BK) channel in pulmonary arterial smooth muscle cells (847.3)

We reported an upregulation of an oxygen-insensitive splice variant of the high-conductance Ca2+-activated K+ (BK) channel in pulmonary arteries (PA) from rats with chronic hypoxia (CH)-induced pulmonary hypertension (PH). This finding infers that the BK channel may represent a vasodilator target for the treatment of PH. However, the BK channel in pulmonary arterial smooth muscle cells (PASMCs) reportedly shows low Ca2+-sensitivity due to uncoupling of the α-subunit pore from the requisite accessory β1 subunit. The goal of this study was to: i) define the Ca2+-sensitivity of the BK channel in rat PASMC, and ii) evaluate if a BK channel opener that relies on the β1 subunit activates BK channels in PASMCs. Whole-cell K+ current in patch-clamped PASMCs from normoxic (N) and CH rats failed to reveal BK current, although it was observed under the same conditions in cerebral ASMCs. However, the Ca2+-sensitivity of BK channels in inside-out patches from PASMCs and cerebral ASMCs exposed to a range of free Ca2+ c...