Radioimmunoassay of Gastrin

Radioimmunoassays have recently made it possible to measure the concentration of gastrin in human plasma (Hansky and Cain, 1969; Byrnes, Young, Chisholm, and Lazarus, 1970; McGuigan and Trudeau, 1970; Yalow and Berson, 1970). It has been shown that the plasma gastrin rises in response to such stimuli as the ingestion of food and insulin hypoglycaemia. However, little is known about any quantitative relationships which may exist between plasma gastrin levels and gastric acid secretion. There is no direct method of measuring gastric secretion in man following a normal meal, and the response to insulin hypoglycaemia may involve both direct vagal stimulation of acid secretion and indirect stimulation mediated by gastrin. It would, therefore, be useful if a test could be devised in which antral gastrin release was powerfully stimulated and in which plasma gastrin levels and gastric acid secretion could be simultaneously measured. The 'antral function test' of Giles and Clark (1966) appears to meet these requirements. In this test, a meat extract (Oxo) is instilled into the stomach via a nasogastric tube, left there for 15 minutes, and removed by aspiration. Afterwards there is usually a marked stimulation of gastric acid secretion which can be followed by continuous aspiration of gastric juice. In experiments reported in this paper we have used such a test (hereafter called the 'Oxo test') to relate gastric acid secretion to plasma gastrin levels. The results have been compared with those obtained in the same subjects either by feeding a standard meal or by provoking insulin hypoglycaemia.