Exposure to ionizing radiation modifies neurally-evoked electrolyte transport and some inflammatory responses in rat colon in vitro

Purpose: To characterize the responsiveness of the colon to neural stimulation following acute exposure of rats to gamma-radiation and to correlate observed changes to a number of parameters. Materials and methods: Rats were exposed to 5 or 10 Gy Cs-137 gamma- radiation or not (sham-irradiated) and studied at 1, 3 and 7 days after irradiation. Stripped segments of colon were mounted in Ussing chambers for measurements of neurally-evoked electrolyte transport (electrical field stimulation). Colonic tissue was also taken for biochemical (tissue 5-hydroxytryptamine, histamine, leukotriene B-4, nitric oxide synthase) and histological analyses (mast cells). Results: In irradiated rats both proximal and distal colon were hyporesponsive to electrical field stimulation at 1 and 3 days, but had recovered by 7 days. In the distal colon, carbachol responses were attenuated 1 day after 10 Gy. Mast cells, tissue histamine and leukotriene B, synthesis were significantly reduced at all time points but no changes were seen in 5-HT or inducible NOS activity. Conclusions: Rat colon becomes hyporesponsive to neural stimuli post-irradiation. The response initially (1 and 3 days) correlates with decreased mast cells and histamine, but not at 7 days.