The detection and measurement of circulating gastrin-like activity by bioassay

A perfused rat stomach technique which can detect synthetic human gastrin I in amounts greater than 10 ng and measure by block assay amounts greater than 50 ng was used to study circulating gastrin-like activity in normal subjects, patients with peptic ulcer, and patients with the Zollinger-Ellison syndrome. No detectable activity was found in normal subjects or patients with gastric ulcer before or after meals. No activity was found in the fasting plasma of patients with duodenal ulcer but after meals activity could be detected in duplicate samples in seven of 20 patients. In nine proven cases of the Zollinger-Ellison syndrome, gastrin-like activity in the plasma ranged from 15 to 356 ng/ml. The gastrin-like content of two tumours was 6.4 and 29.1 mug/g of tissue. The significance of these findings in relation to immunoassay is described.