Effects of a tyrosine phosphatase inhibitor on chloride secretion in humanintestinal epithelia

AIMS: transcellular chloride transport is the key event underlying epitheli al hydration in the intestine. Little is known about the role of protein ty rosine phosphatases in the regulation of basal and stimulated secretion in human intestinal epithelia. The aim of our study was to investigate the eff ects of the protein tyrosine phosphatase inhibitor sodium orthovanadate on vectorial chloride transport in native human colon. METHODS: an electrophysiological technique was used to measure changes in s hort-circuit current via a dual voltage/current clamp in native human colon mucosa and in T84 (ATCC) human intestinal cells mounted in modified Ussing chambers. RESULTS: orthovanadate (1 mM) added to the serosal side of native human col on caused a net rise in short circuit current, reflecting the stimulation o f serosal-to-mucosal chloride movement. Epithelial cells responded similarl y to the same concentration of the compound. The stimulatory effect of orth ovanadate was enhanced by pretreatment with the tyrosine kinase inhibitor g enistein, but only when orthovanadate was added to the basolateral chamber. In contrast, the synergistic interaction did not occur when epithelial cel ls were previously exposed to the cAMP agonist forskolin. CONCLUSIONS: we show that tyrosine phosphatases may be involved in the regu lation of epithelial chloride transport, and that orthovanadate stimulates secretion in the human colon.