Activation of an adenosine 3 ',5 '-cyclic monophosphate-dependent Cl- conductance in response to neurohormonal stimuli in mouse endometrial epithelial cells: The role of cystic fibrosis transmembrane conductance regulator

Previous studies have demonstrated that Cl- secretion by the mouse endometr ial epithelium is under neurohormonal influence. The present study characte rized the Cl- conductance activated by a number of agonists in the mouse en dometrial epithelial cells using the whole-cell voltage-clamp technique. Ad renaline (1 mu M), prostaglandin (PG) E-2 (5-10 mu M), and PGF(2 alpha) (10 0 mu M) activated a whole-cell current that exhibited a linear I-V relation ship as well as time- and voltage-independent characteristics. However, the current magnitude varied with different agonists. The agonist-activated cu rrent could be mimicked by an adenylate cyclase activator, forskolin (10 mu M), and suppressed by an adenylate cyclase inhibitor, MDL12330A, suggestin g the involvement of cAMP. Current characteristics remained the same after cation replacement, leaving Cl- as the major permeant ion species in the so lutions. The reversal potential of the agonist-induced current was close to the equilibrium potential of Cl- in the presence of a Cl- gradient, indica ting the activation of Cl- conductance. The agonist-induced current was inh ibited by the Cl- channel blocker diphenylamine 2,2'-dicarboxylic acid (DPC ), but not by the Cl- channel blocker 4,4'-diisothiocyanatostibene-2,2'-dis ulfonic acid (DIDS). The anion selectivity sequence of the current was NO3- >Br->Cl->I-. The observed electrophysiological properties of the agonist-in duced Cl- conductance were consistent with those reported for the cystic fi brosis transmembrane conductance regulator (CFTR), a cAMP-activated Cl- cha nnel expressed in many epithelia. The expression of CFTR in the mouse endom etrial cells was also demonstrated by Western blot analysis. It appears tha t neurohormonal regulation of the uterine fluid in the mouse endometrium co nverges on the cAMP-activated Cl- channel, presumably CFTR.