Effects of insulin-like growth factor-I administration on radiation enteritis in rats. 
Acute radiation-induced damage to the small bowel occurs frequently during abdominal radiotherapy.  Since the small intestine is selectively responsive to the growth-promoting effects of insulin-like growth factor-I (IGF-I), we investigated the effects of IGF-I administration on mucosal recovery from radiation enteritis in the rat.  Rats received a single 10-Gy dose of total abdominal irradiation followed by implantation of mini-pumps infusing either IGF-I or vehicle for 4 days.  After the rats had been killed, gut organs were weighed before light microscopic and biochemical examination.  Irradiated rats receiving IGF-I lost less body weight than vehicle-treated rats, whereas the wet weights of the stomach, small intestine, and colon were increased by 10%, 19%, and 21%, respectively, and crypt depth was increased in the duodenum, jejunum, and ileum.  IGF-I administration after abdominal irradiation increased small-intestinal mass and improved indicators of mucosal integrity, suggesting acceleration of small-intestinal mucosal recovery from radiation injury.