The occurrence of gastrin-17 in the heart.

Radioimmunoassay revealed gastrin-like immunoreactivity in extracts of the heart muscle from cat, guinea pig, rabbit and hog. The immunoreactivity was unevenly distributed, the highest levels being observed in extracts from the atria of the cat heart: in the right atrium approximately 1,000 pg/g or 450 pmol/kg and in the left atrium approximately 4,400 pg/g or 2,000 pmol/kg. In extracts from the cat atria the gastrin-like immunoreactivity was identified as Gastrin-17. The preponderant localization of gastrin to the atria is suggested to be due to the distribution of gastrin containing vagal fibres and nerve terminals in that area, even if a possible localization to specific receptors, Purkinje fibres etc. cannot be excluded. A modulating action on the vagal influence on the heart, either on neurotransmission or on the receptor level, or a direct (perhaps trophic) effect on biochemical processes in the muscle are suggested as possible biological functions of the heart gastrin.