Regulation of antral gastrin content

Five groups of rats were fasted for 3 days and injected with either NaCl or 5, 10, 20, or 40 micrograms/kg bombesin every 8 h. The animals were killed, and their serum and antral gastrin levels were compared with those of normally fed rats. Fasting reduced serum gastrin to 14% of control; antral gastrin was reduced to 21% of control. All doses of bombesin significantly increased serum gastrin in fasted rats, and 20 and 40 micrograms/kg significantly increased antral gastrin. A group of normally fed rats was also compared with one fed a liquid diet for 7 days. Half of each of these was injected with 20 micrograms/kg bombesin (3 times/day) and the other half with NaCl. Bombesin significantly increased serum and antral gastrin in the rats fed solid food. The liquid diet lowered serum and antral gastrin to 17 and 59% of control values, respectively. Bombesin injection totally prevented these decreases. These data indicate that food in the gastrointestinal tract is not required for either gastrin release or synthesis. Furthermore, the data suggest that gastrin synthesis is regulated primarily by gastrin release or by direct stimulation by bombesin rather than by specific food products.