Mucin secretion by the human colon cell line LS174T is regulated by bile salts

We recently reported that bile salts play a role in the regulation of mucin secretion by cultured dog gallbladder epithelial cells. In this study we h ave examined whether bile salts also influence mucin secretion by the human epithelial colon cell line LS174T. Solutions of bile salts were applied to monolayers of LS174T cells. Mucin secretion was quantified by measuring th e secretion of [H-3]GlcNAc labeled glycoproteins, Both unconjugated bile sa lts as well as taurine conjugated bile salts stimulated mucin secretion by the colon cells in a dose-dependent fashion. Hydrophobic bile salts were mo re potent stimulators than hydrophilic bile salts. Free (unconjugated) bile salts were more stimulatory compared with their taurine conjugated counter parts. Stimulation of mucin secretion by LS174T cells was found to occur at much lower bile salt concentrations than in the experiments with the dog g allbladder epithelial cells. The protein kinase C activators PMA and PDB ha d no stimulatory effect on mucin secretion, We conclude that mucin secretio n by the human colon epithelial cell line LS174T is regulated by bile salts . We suggest that regulation of mucin secretion by bile salts might be a co mmon mechanism, by which different epithelia protect themselves against the detergent action of bile salts, to which they are exposed throughout the g astrointestinal tract.