IN-VIVO ALTERATIONS OF FLUID AND ELECTROLYTE FLUXES IN RAT COLON BY GAMMA-IRRADIATION

Colonic function in rats was investigated up to 14 days following expo sure to whole-body gamma irradiation (8 Gy) using a combination of in vivo and in vitro approaches. Water and electrolyte fluxes were measur ed in vivo under anesthesia by insertion of an agarose cylinder into t he descending colon. Short-circuit current responses (I-sc; basal, ago nist-stimulated) of distal colon were measured in vitro as were mannit ol and sodium fluxes. Water and electrolyte absorption (Na, Cl) was ma rkedly reduced at four days after irradiation but returned to normal a t seven days. Potassium secretion was increased from one to seven days after exposure. There were no differences in basal I-sc, Na, or manni tol fluxes at four days but responses to secretagogues (5-hydroxytrypt amine, forskolin, carbachol) were attenuated. No morphological alterat ions were associated with these functional modifications.