Radiation decreases murine small intestinal HCO3- secretion.

Purpose: While secretagogue-induced diarrhea is rich in chloride (Cl(-)) and bicarbonate (HCO(3) (-)) anions, little is known about diarrhea or its anionic composition following irradiation. We performed studies to characterize the differences between cyclic adenosine monophosphate (cAMP)-stimulated anion secretions in irradiated and non-irradiated mice.
Materials and Methods: HCO(3) (-) secretion was examined in basal, cAMP-stimulated, and irradiated jejunal tissues from BALB/c (Bagg albino) mice. The abdomens of the mice were γ-irradiated using a caesium-137 source.
Results: Ussing-chamber experiments performed in an HCO(3)(-)-containing, Cl(-)-free solution on the bath side showed inhibition of HCO(3)(-) in irradiated mice. Non-irradiated mice exhibited bumetanide-sensitive and insensitive current, while irradiated mice displayed bumetanide-sensitive current. pH-stat experiments showed inhibition of basal and cAMP-stimulated HCO(3)(-) secretions in irradiated mice. Immunohistochemistry and Western blot analysis displayed a sodium-bicarbonate cotransporter expression in the villus and not the crypt of non-irradiated mice, while its expression and protein levels decreased in irradiated mice.
Conclusions: Anion secretions in irradiated mice, being primarily Cl(-) and minimally HCO(3)(-), differ from that of secretagogue-induced anion secretions. Understanding anion loss will help us correct electrolyte imbalances, while reduced HCO(3)(-) secretion in the upper-gastrointestinal tract might also have implications for irradiation-induced nausea and vomiting.