Activation of intestinal Na-K-2Cl cotransport by 5′-amp requires F-actin remodeling

Background Although cyclic adenosine monophosphate (cAMP)-dependent intestinal chloride ion (Cl-) secretion is regulated primarily at the level of apical Cl- channels, cAMP also elicits basolateral microfilament remodeling and activates basolateral sodiumpotassium-2 chloride (Na-K-2Cl) cotransport. Without these additional events, secretion is inhibited. However, it is unclear whether microfilament-dependent activation of Na-K-2Cl cotransport is a direct effect of cAMP or a secondary response to the opening of apical Cl- channels. Methods Using the human intestinal epithelial cell Une T84, we examined Cl- secretion elicited by 5′-adenosine monophosphate (5′-AMP), a novel agonist that activates apical Cl- channels without elevation of intracellular cAMP. Results 5′-AMP was found to activate basolateral Na-K-2Cl cotransport, but such regulation was abolished by the actin stabilizer, phalloidin. Conclusions Basolateral Na-K-2Cl cotransport appears to be regulated, at least in part, as an indirect response to activation of apical Cl- channels, a pathway of regulation which may require cytoskeletal remodeling