Female Gender-specific Inhibition of KCNQ1 Channels and Chloride Secretion by 17β-Estradiol in Rat Distal Colonic Crypts

The estrogen sex steroid 17β-estradiol rapidly inhibits secretagogue-stimulated cAMP-dependent Cl– secretion in the female rat distal colonic crypt by the inhibition of basolateral K+ channels. In Ussing chamber studies, both the anti-secretory response and inhibition of basolateral K+ current was shown to be attenuated by pretreatment with rottlerin, a PKCδ-specific inhibitor. In whole cell patch-clamp analysis, 17β-estradiol inhibited a chromanol 293B-sensitive KCNQ1 channel current in isolated female rat distal colonic crypts. Estrogen had no effect on KCNQ1 channel currents in colonic crypts isolated from male rats. Female distal colonic crypts expressed a significantly higher amount of PKCδ in comparison to male tissue. PKCδ and PKA were activated at 5 min in response to 17β-estradiol in female distal colonic crypts only. Both PKCδ- and PKA-associated with the KCNQ1 channel in response to 17β-estradiol in female distal colonic crypts, and no associations were observed in crypts from males. PKA activation, association with KCNQ1, and phosphorylation of the channel were regulated by PKCδ as the responses were blocked by pretreatment with rottlerin. Taken together, our experiments have identified the molecular targets underlying the anti-secretory response to estrogen involving the inhibition of KCNQ1 channel activity via PKCδ- and PKA-dependent signaling pathways. This is a novel gender-specific mechanism of regulation of an ion channel by estrogen. The anti-secretory response described in this study provides molecular insights whereby estrogen causes fluid retention effects in the female during periods of high circulating plasma estrogen levels.