Biosynthesis of tyrosine O-sulfated gastrins in rat antral mucosa.

Biosynthetic incorporation of labeled amino acids into the major gastrins in rat antrum, Component I, gastrin 34 ("big" gastrin), and gastrin 17-like peptides ("little" gastrin) was demonstrated after in vitro incubation of antral mucosal slices. The antral gastrin synthesis was stimulated by fundectomy, which ablates gastric acid secretion and thereby increases the gastrin concentration in plasma 20-fold. Tyrosine O-sulfation of gastrin was also demonstrated by incorporation of [35S]sulfate. Sulfate-labeled peptides precipitated by gastrin antisera coeluted with sulfated gastrin immunoreactivity on ion-exchange chromatography. Aryl-sulfatase treatment removed the [35S]sulfate from labeled gastrin and resulted in a change in elution pattern of the immunoreactivity to that of the unsulfated gastrins. The presence of 35S-labeled tyrosine O-sulfate residues was directly demonstrated by two-dimensional thin-layer electrophoresis after alkaline hydrolysis of [35S]sulfate-labeled gastrin. All the antral gastrins incorporated [35S]sulfate.