BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 72-77 PROGASTRIN-LIKE IMrlUNOREACTIVITY IN PORCINE ANTRUM: IDENTIFICATION AND CHARACTEkIZATION WITH REGION-SPECIFIC ANTISERA

In an effort to identify and characterize precursors of gastrin in tissues, we generated region-specific antisera against a synthetic progastrin peptide, Tyr-Gly-Trp-Met-Asp-Phe-Gly-Arg-Arg (GL9), as deduced from the nucleotide sequence of gastrin mRNA. This antisera did not cross-react with gastrin or progastrin peptides with shorter carboxyl-terminal extensions. Progastrin-like imnunoreactivity (PGLI) was measured in porcine antrum at a concentration of 6.8 f 1.2 pmol/g wet weight (mean f SE, n = 5), or roughly 0.2% of that of gastrin. On Sephadex 650 chromatography, a major peak of PGLI was eluted as a slightly larger molecule than gastrin heptadecapeptide (617) but possessed the same N-terminal imnunoreactivity. These findings suggest that 617 may be formed by processing of a carboxyl-terminally extended precursor as an alternative to cleavage of big gastrin (634).