Abstract
Summary
Bombesin was administered to young fasted rats, and blood levels of immunoreactive gastrin and calcitonin (CT) were measured. Doses of bombesin up to 100 μg/rat i.v. did not affect serum calcium or phosphorus. Five minutes after bombesin, 10 or 50 μg/rat, serum gastrin increased 1- to 2-fold and, by 30 min, it was elevated 5- to 10-fold. Time-course and dose-response studies showed that doses of 10–100 μg/rat increased gastrin and that gastrin rose within 5 min after 50 μg/rat and remained elevated for at least 2 hr. Despite bombesin-induced hyper-gastrinemia, CT remained low or undetectable (<50–100 pg/ml) at all times. In one study, somatostatin (50 μg/rat i.v.), given together with bombesin, inhibited the rise in serum gastrin by 50%, but serum CT, which was detectable, was unaffected by either bombesin or somatostatin. We conclude that bombesin stimulates gastrin release in the rat, but the elevated gastrin does not promote CT secretion. The results support our earlier findings which indicate that gastrin is weak or ineffective in the rat as a CT secretagogue.
The technical assistance of Ms. Deloris B. Alston and Ms. Lillie T. Williams is gratefully acknowledged.
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