In vitro activity: Lubiprostone induces a robust secretory response in T84 monolayers. Lubiprostone induces a rise in cAMP levels that was sensitive to EP(4)-receptor blockage in T84 cells. Lubiprostone induces a contraction in rat and human stomach longitudinal muscle, which is inhibited by pretreatment with the EP(1) receptor antagonist but not by the EP(3) or EP(4) receptor antagonists. Lubiprostone also reduces electrically stimulated, neuronal contractions in rat and human colon circular muscle preparations. Lubiprostone (1 mM) stimulates higher elevations in TER despite lower I(sc) responses compared with the nonselective secretory agonist PGE(2) (1 mM).

Cell Assay: Lubiprostone significantly reduces mucosal-to-serosal fluxes of (3)H-labeled mannitol to levels comparable to those of normal control tissues and restored occludin localization to tight junctions. Lubiprostone causes comparable and maximal increases of I(sc) in T84 cells. Lubiprostone-induced increases in iodide efflux are ~80% of those obtained with forskolin. Lubiprostone activates Cl(-) secretion in T84 cells via cAMP, protein kinase A, and by increasing apical membrane CFTR protein. Lubiprostone, applied to the small intestinal mucosa in eight concentrations ranging from 1-3000 nM, evokes increases in Isc in a concentration-dependent manner with an EC50 of 42.5 nM. Lubiprostone applied to the mucosa of the colon in eight concentrations ranging from 1-3000 nM evokes increases in Isc in a concentration-dependent manner with an EC50 of 31.7 nM.