Long-term effects of X-irradiation on gastrointestinal function and regulatory peptides in monkeys

Purpose: To investigate the long-term effects of X-irradiation on different aspects of gastrointestinal function in the non-human primate (Macaca mula tta). Materials and methods: Animals were exposed to X-radiation (5 or 6 Gy) or n et (sham) and gastrointestinal function was investigated 4-6 years after ex posure. Basal and agonist-stimulated short circuit current (Isc) responses were measured in isolated jejunum. Intestinal tissue was taken for histolog ical analysis as well as for determination of mucosal marker enzyme activit ies and gastrointestinal regulatory peptide levels. Vasoactive intestinal p eptide receptor characteristics were determined as well as VIP-stimulated I se responses. GI peptides were also measured in plasma. Results: Few differences were seen in basal electrical parameters or tissue morphology but there was a tendency for reduced basolateral membrane enzym e activity. VIP-stimulated Isc responses were reduced in irradiated animals as were VIP-stimulated adenylate cyclase responses. Plasma and tissue (ile al and colonic muscle layers) gastrin releasing peptide levels were increas ed in irradiated animals. In contrast circulating gastrin levels were lower . Conclusions: Late effects of total-body irradiation on GI function in monke ys showed altered circulating and tissue levels of some GI peptides. In add ition the biological effects of vasoactive intestinal peptide were modified .