Bombesin-like peptides in mammals.

Acid extracts of rat gut and brain contain substances that cross-react in a radioimmunoassay for the amphibian skin tetradecapeptide bombesin. Highest concentrations are present in the fundic part of the stomach, but there are significant amounts throughout the small and large intestine. Concentrations in the brain are highest in the hypothalamus. On gel filtration the rat bombesin-like immunoreactivity eluted as two major peaks. Fractionation of the second peak on cation exchange chromatography resolves this material into two further components. Intravenous infusions of partially purified preparations of the two components separated on gel filtration cause increases in serum gastrin in rats that are similar to those produced by immunochemically comparable amounts of synthetic bombesin.