Depolarization of osteoclast plasma membrane potential by 17β-estradiol

The effect of estrogen on plasma membrane potential of isolated avian osteoclasts was examined through the use of a fluorescent potential-sensitive dye, bis-(1,3-dibutylbarbiturate) trimethine oxonol, also known as bis-oxonol. A decrease in potential was observed within seconds of addition of 17 beta-estradiol, Ouabain, a specific Na+K+-ATPase inhibitor, and BaCl2, an inhibitor of the inwardly rectifying K+ channel, blocked the estrogen response, Verapamil and lanthanum chloride (LaCl3), inhibitors of inward Ca2+ channels, and 4'4-diisothiocyanatostilbene-2'2-disulfonic acid (DIDS), an inhibitor of CT channels, did not affect the depolarization. Herbimycin A, a tyrosine kinase inhibitor, also had no effect on the decreased membrane potential. These data provide evidence which suggests that estrogen regulates osteoclasts through ion channel activities, The change in K+ channel activity was observed within seconds of addition of 17 beta-estradiol, indicating an action at the level of the plasma membrane.