Effect of bombesin on the development of the neonatal rabbit gastrointestinal tract

The effect of bombesin on the postnatal development of the gastrointestinal tract was examined in New Zealand white rabbits. Bombesin (1.25, 12.5, 30 micrograms/kg body weight) or vehicle was administered intraperitoneally to suckling rabbits for 13 days starting on day 4 of life. The animals were killed at day 17. There was no significant effect of bombesin at doses of 1.25 or 12.5 micrograms/kg in any region of the gut studied. Bombesin administered at 30 micrograms/kg induced a widespread trophic effect in the gastrointestinal tract characterized by significant increases in the wet weight of the stomach, liver and whole small intestine, as well as in 10-cm segments of the proximal, middle, and distal small intestine. There was also a significant increase in the mucosal weight of 10-cm segments of the proximal, middle and distal small intestine, and the colon in the bombesin-treated group. Bombesin significantly increased the protein and DNA contents of the liver, the fundus of stomach, all segments of the small intestine and the distal colon. Maximal stimulation was seen in DNA content, suggesting that bombesin has a primarily hyperplastic effect. Bombesin increased the activities of small intestinal sucrase and maltase but not lactase. Bombesin did not alter hepatic glucokinase activity. These findings suggest that bombesin can promote the growth of the neonatal rabbit gastrointestinal tract and liver.