, Volume 156, Issue 1, pp 45-52

Regulation of Cl Secretion by Extracellular ATP in Cultured Mouse Endometrial Epithelium

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Abstract.

The present study explored regulation of electrogenic ion transport across cultured mouse endometrial epithelium by extracellular ATP using the short-circuit current (I SC ) and the patch-clamp techniques. The cultured endometrial monolayers responded to apical application of ATP with an increase in I SC in a concentration-dependent manner (EC50 at 3 μm). Replacement of Cl in the bathing solution or treatment of the cells with Cl channel blockers, DIDS and DPC, markedly reduced the I SC , indicating that a substantial portion of the ATP-activated I SC was Cl-dependent. Amiloride at a concentration (10 μm) known to block Na+ channels was found to have no effect on the ATP-activated I SC excluding the involvement of Na+ absorption. Adenosine was found to have little effect on the I SC excluding the involvement of P1 receptors. The effect of UTP, a potent P2U receptor agonist on the I SC was similar to that of ATP while potent P2X agonist, α-β-Methylene adenosine 5′-triphosphate (α-β-M-ATP) and P2Y agonist, 2-methylthio-adenosine triphosphate (2-M-ATP), were found to be ineffective. The effect of ATP on I SC was mimicked by the Ca2+ ionophore, ionomycin, indicating a role of intracellular Ca2+ in mediating the ATP response. Confocal microscopic study also demonstrated a rise in intracellular Ca2+ upon stimulation by extracellular ATP. In voltage-clamped endometrial epithelial cells, ATP elicited a whole-cell Cl current which exhibited outward rectification and delayed activation and inactivation at depolarizing and hyperpolarizing voltages, respectively. The results of the present study demonstrate the presence of a regulatory mechanism involving extracellular ATP and P2U purinoceptors for endometrial Cl secretion.