Radiation decreases murine small intestinal HCO3- secretion

Purpose: While secretagogue-induced diarrhea is rich in chloride (Cl-) and bicarbonate (HCO3-) 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: HCO3- secretion was examined in basal, cAMP-stimulated, and irradiated jejunal tissues from BALB/c (Bagg albino) mice. The abdomens of the mice were gamma-irradiated using a caesium-137 source. Results: Ussing-chamber experiments performed in an HCO3--containing, Cl -free solution on the bath side showed inhibition of HCO3- 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 HCO3- 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 HCO3-, differ from that of secretagogue-induced anion secretions. Understanding anion loss will help us correct electrolyte imbalances, while reduced HCO3- secretion in the upper-gastrointestinal tract might also have implications for irradiation-induced nausea and vomiting.