Effect of rhein on electrogenic chloride secretion in rabbit distal colon

The effect of the laxative component rhein on electrical properties and Cl transport was investigated in partially stripped epithelial sheets of rabbit distal colon under short-circuit conditions. Whereas mucosal rhein had no effect, serosally applied rhein stimulated electrogenic Cl secretion in a dose-dependent manner with a half-maximal stimulation at 0.05 mmol/l. The stimulation was partially reversible by serosal bumetanide. Indomethacin preincubation inhibited the effect of rhein, but did not prevent theophylline-induced Cl secretion. The results suggest a prostaglandin-mediated effect of rhein on the apical Cl conductance of the colonic cells.