Molecular forms of gastrin in antral mucosa of the horse

The predominant form of gastrin in the antral mucosa of the stomach of virtually all species previously examined is the 17 amino acid peptide little gastrin (G17). This report describes the occurrence in equine antral mucosa of an immunoreactive form of gastrin with elution properties on Sephadex G-50 superfine similar to human unsulfated big gastrin (G34-I). This putative equine big gastrin was a major component of the gastrin immunoreactivity present. A second peak of activity in equine antral mucosa eluted in an identical manner to human little gastrin (hG17-I). Inhibition curves of equine big and little gastrin, with the gastrin radioimmunoassay utilized in this study, were parallel. This observation indicates that there was no spurious increase in the apparent relative amount of big gastrin due to significant differences in the RIA antibody cross-reactivity to big and little equine gastrin. The equine big gastrin peak was resolved by ion exchange chromatography into unsulfated and sulfated forms in approximately equal amounts. This data implies that posttranslational processing of gastrin in horses may differ from that of species previously studied.