The effect of whole-body radiation on blood levels of gastrointestinal peptides in the rat.

Radiation-induced injury may occur in various incidents as well as the terrorist radiation exposure scenario. The digestive tract is among the most radiosensitive organs in the body and its function, which is partly regulated by gastrointestinal (GI) peptides, can be affected by radiation exposure. However, very little is known about the effect of whole-body radiation on blood GI peptides. The aim of this study therefore was to determine the effect of whole-body radiation on circulating levels of GI peptides in the rat. To study this, rats were exposed to 5-Gy whole-body gamma radiation. They were then euthanized at 1, 2, 4, or 8 days after irradiation. Plasma levels of cholecystokinin (CCK), secretin, gastrin, and ghrelin were determined using specific enzyme immunoassays. Serum levels of alanine transaminase (ALT), alkaline phosphatase (ALP), total bilirubin, and lactate were also measured. Our results showed that whole-body irradiation significantly decreased plasma CCK levels by 57% and 54% at 1 and 2 days after irradiation (P<0.05), respectively. At 4 and 8 days after irradiation, plasma CCK levels returned to normal. Similarly, plasma levels of secretin decreased by 48% at 2 days after irradiation (P<0.05), and returned to normal at 8 days after irradiation. In contrast, there was no significant change in plasma levels of gastrin and ghrelin after irradiation. No significant differences were observed in ALT, ALP, total bilirubin, or lactate. In conclusion, whole-body radiation exposure alters blood GI peptides especially the ones that were produced in the small intestine, such as CCK and secretin. The diverse response of the GI peptides to irradiation could be due to a difference in radiosensitivity in different regions of the GI tract.