Non-genomic action of 17beta-estradiol on opening of Ca(2+)- and voltage-activated K+ channel in lacrimal acinar cells.

The effect of the sex hormone 17 beta-estradiol on the opening of Ca(2+)- and voltage-activated K+ channels (BK channels) in the basolateral plasma membrane of mouse lacrimal acinar cells was studied by patch-clamp single-channel recording and Ca(2+)-measurement using fura-2 AM. In intact cells (the cell-attached configuration) using a pipette containing a Na+ -rich solution, estradiol was added to the bath solution, which does not have direct contact with the electrically isolated areas of membrane patch from which the single-channel currents were recorded. Estradiol increased the frequency of opening of the BK channels within a few minutes after its application. The effect of estradiol on the opening of the BK channels in acinar cells in male mice was greater than that in females. In Ca(2+)-measurement using fura-2 AM, estradiol did not increase the level of intracellular Ca2+ during a 5-minute observation period. The application of estradiol with propranolol, a beta-adrenergic receptor blocker, did not increase BK channel opening. The application of estradiol with Rp-cAMPS, an inhibitor of cyclic AMP-dependent protein kinase (protein kinase A), also inhibited the increase in channel opening. The addition of a catalytic unit of protein kinase A to the inside of the excised membrane patch increased the frequency of opening of the BK channels. These results suggest that estradiol interacts with beta-adrenergic receptor on the basolateral membrane and regulates the opening of BK channels by protein phosphorylation via a cyclic AMP pathway, without a change in the Ca2+ level.