Effects of quercetin on epithelial chloride secretion.

The effect of the flavonoid quercetin on epithelial chloride secretion has been studied in vitro. These studies were performed using monolayers of the human colonic epithelial cell line T84, mounted in modified Ussing chambers. Chloride secretion was assessed as changes in short circuit current (I(SC)) both in basal conditions as well as in response to different secretagogues: carbachol (100 microM), vasoactive intestinal polypeptide (VIP) (10 nM) and prostaglandin E2 (1 microM). Secretion was also induced via protein kinase C by adding phorbol myristate acetate (PMA, 100 nM) in the presence of the calmodulin inhibitor W13 (50 microM). Quercetin (100 microM) was able to promote secretion when the flavonoid was added to the mucosal side of the monolayer. On the contrary, serosal addition of quercetin was devoid of secretory activity and at concentration of 10 microM it was able to inhibit chloride secretion in response to carbachol, prostaglandin E2 and PMA/W13, but not that induced by VIP. We conclude that the effect of quercetin on epithelial chloride secretion is dual, secretory and antisecretory, depending on both the concentration and the side of the monoloayer where the addition of the flavonoid is made.