Dose dependence effects of ionizing radiation on bile acid metabolism in the rat

Purpose: To study radiation dose-related changes of individual or total bil e acids in various physiological fluids in order to identify potential bio- indicators of radiation-induced gastrointestinal injuries. Materials and methods: Wistar rats were sham- or whole-body gamma irradiate d (1-12 Gy). Total and individual bile acids were quantified, 3 days after exposure, in bile collected after catheterization of the bile duct. Total b ile acid concentrations were also measured in plasma and colonic contents 1 , 2 and 3 days after irradiation. These concentrations were determined by a n enzymatic method whereas individual bile acids were quantified by HPLC. Results: In bile, whereas total bile acid concentration remained unchanged after irradiation whatever the dose, the proportion of dihydroxy bile acids in the pool of total bile acids was gradually increased with the irradiati on dose, especially from 8 Gy. In plasma samples, total bile acid concentra tions fell for doses higher than 10 Gy. In colonic contents, bile acid conc entrations increased progressively with time (from 1 to 3 days) and with ir radiation dose (from 1 to 12 Gy), reaching a plateau 3 days after exposure for doses higher than 10 Gy. Conclusions : These results show that changes in colonic bile acid concentr ations which are reflected in faeces are perhaps a useful parameter to impr ove diagnosis and prognosis of radiation-induced gastrointestinal damage si nce it probably reflects directly intestinal bile acid malabsorption.