title: Bioassay of gastrin, using the totally isolated, vascularly perfused rat stomach. A biomodel sensitive to gastrin in physiological concentrations.
abstract: A bioassay sensitive to gastrin (G 1-17) in physiological concentrations and suitable for testing of biological activity of minor amounts of radioiodinated gastrin is reported. G 1-17 was iodinated by a gentle Iodo-gen method and purified to high specific activity (1900 Ci/mmol). Totally isolated vascularly perfused rat stomachs were prepared and stimulated by graded amounts of G 1-17. Gastrin 'dose'-dependently increased the acid output from 5.7 +/- 1.0 mueq/40 min (basal) to a maximum of 58.8 +/- 10.0 mueq/40 min at a concentration of 520 pmol/l in the vascular perfusate. The lowest G 1-17 concentration that significantly increased the acid output from the basal value was 65 pmol/l, corresponding to a dose of 17.5 ng/stomach-hour. 125I-G 1-17 also increased the acid output significantly at this threshold dose. The amount of lactic acid enzymatically determined in the luminal perfusate was negligible, indicating a true parietal cell stimulation. Accordingly, a very sensitive bioassay for gastrin, suitable for testing of biological activity of G 1-17 and 125I-G, is described. Significant acid responses were obtained with physiological concentrations of gastrin, requiring less than 100 ng of hormone and labelled hormone, respectively, to show biological activity.
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods*; D005744:Gastric Acid / Q000378:metabolism; D005755:Gastrins / Q000032:analysis* / Q000494:pharmacology; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007773:Lactates / Q000096:biosynthesis; D019344:Lactic Acid; D008297:Male; D008954:Models, Biological; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013270:Stomach / Q000502:physiology*
chemical_list: D005755:Gastrins; D007457:Iodine Radioisotopes; D007773:Lactates; D019344:Lactic Acid; C013550:gastrin 17