Modulation of the BK Channel by estrogens: examination at a single channel level

BK channels regulate vascular tone by hyperpolarizing smooth muscle in response to fluctuating calcium concentrations. Oestrogen has been reported to lower blood pressure by increasing BK channel open probability through direct binding to the regulatory 1-subunit(s) associated with the channel. The present investigation demonstrates that 17-oestradiol activates the BK channel complex by increasing the burst duration of channel openings. A subconductance state was observed in 25% of recordings following the addition of 17-oestradiol and could reflect uncoupling between the pore forming 1-subunit and the regulatory 1-subunit. We also present evidence that more than one 1-subunit is required to facilitate binding of 17-oestradiol to the channel complex