ACTIVATION OF INTESTINAL NA-K-2CL COTRANSPORT BY 5'-AMP REQUIRES F-ACTIN REMODELING

BACKGROUND: Although cyclic adenosine monophosphate (cAMP)-dependent i ntestinal chloride ion (Cl-) secretion is regulated primarily at the l evel of apical Cl- channels, cAMP also elicits basolateral microfilame nt remodeling and activates basolateral sodium-potassium-2 chloride (N a-K-2Cl) cotransport. Without these additional events, secretion is in hibited. However, it is unclear whether microfilament-dependent activa tion 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 hu man intestinal epithelial cell line T84, we examined Cl- secretion eli cited by 5'-adenosine monophosphate (5'-AMP), a novel agonist that act ivates apical Cl- channels without elevation of intracellular cAMP. RE SULTS: 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 map require cytoskeletal rem odeling.