Antibodies to the N-terminus of human Gastrin-34 react with material in rat and ferret brain

Antibodies specific for the N-terminus of human big gastrin, or NT G34, reveal in immunohistochemistry extensive systems of nerve cell bodies and fibres in the rat and ferret brain. However, when the same antibodies were used in radioimmunoassay of rat and ferret brain tissue extracts they failed to reveal immunoreactive material. At least one of the antibodies used for radioimmunoassay could be shown to react with NT G34 in rat pyloric antral extracts. Antibodies specific for other peptides derived from progastrin failed to reveal the systems demonstrated with the N-terminal G34 antibodies. It is concluded that expression of the gastrin gene is unlikely to account for the present observations. Instead we suggest that a novel peptide with low affinity for NT G34 specific antibodies is found in rat and ferret central neurones.