Exposure to ionizing radiation increases responsiveness to neural secretory stimuli in the ferret jejunum in vitro.

ABSTRACT

Experiments were designed to determine the effects of ionizing radiation on jejunal epithelial function in the ferret in vitro. Basal and stimulated electrolyte transport were determined in Ussing chambers at 0.5, 2, 24 and 48 h post-irradiation. Tissue histamine and 5-hydroxytryptamine levels were measured. Myeloperoxidase activity was also measured as an index of inflammation. Basal short circuit current was reduced at 2 h post-irradiation, but was elevated at 48 h. Basal conductance was significantly increased by 24 and 48 h. Responsiveness to electrical field stimulation was depressed at 0.5 h, and was greater than control by 24 and 48 h post-irradiation. Similarly, short circuit current responses to prostaglandin E2 were depressed at 0.5 h and elevated at 24 h. No significant change was observed in the response to carbachol post-irradiation, indicating that alterations in responsiveness were not likely at the level of the enterocyte. Changes in responsiveness to electrical field stimulation correlated significantly with increases in mucosal mast cell numbers. Myeloperoxidase activity, indicative of neutrophil infiltration, did not increase post-irradiation, nor was there histological evidence of an inflammatory cell infiltrate. There were no changes in tissue histamine or 5-hydroxytryptamine. Histology also revealed little microscopic morphological change from shams in tissue from irradiated ferrets. The results of this study demonstrate effects of irradiation on electrolyte transport in the ferret jejunum. The enhanced neurally evoked electrolyte transport observed at 24-48 h post-irradiation was not correlated with the development of inflammation, but was correlated with changes in mast cell numbers.