PEPTIDE YY-INDUCED ALTERATION OF COLONIC ELECTROLYTE TRANSPORT IN THERAT

The effect of peptide YY (PYY) on active electrolyte transport in rat colon was studied under short-circuited conditions. PYY (10(-6) M) dec reased the basal short-circuit current (I-sc) in both the distal and p roximal segments of the colon. The decrease in I-sc induced by PYY in the distal colon was about 3 times larger than that in the proximal co lon. The response to PYY was inhibited by diphenylamine 2-carboxylate, a specific blocker of the Cl-channel, but not by amiloride, a Na-chan nel blocker. Unidirectional flux measurements in the distal colon reve aled that PYY increased the net Na and Cl absorption and decreased the serosal-to-mucosal Cl flux. PYY inhibited the neurally mediated secre tory response to electrical field stimulation in a concentration-depen dent manner. PYY was also shown to reduce the direct action of the cho linergic agonist bethanechol on the epithelium. These results suggest that PYY inhibits electrogenic Cl secretion and stimulates electroneut ral NaCl absorption via both presynaptic and postsynaptic sites in the distal colon.