Bioassay and Radioimmunoassay of Plasma Gastrin in a Case of Zollinger-Ellison Syndrome

Fasting plasma gastrin levels were measured in a patient with the Zollinger-Ellison syndrome by both bioassay and radioimmunoassay. The level remained constant following total gastrectomy, but fell sharply following parathyroidectomy. Although the bioassay gave gastrin levels which were consistently 2 to 3 times higher than those obtained by radioimmunoassay, the values showed a similar trend. However, both methods gave almost identical results for the gastrin contents of antral mucosa and pancreatic tumour samples from the patient. It is suggested that biologically active gastrin-like substances not detectable by radioimmunoassay were present in the patient's plasma.