Assay of gastrin by means of its gastric acid stimulating activity

Comparison of gastrin bioactivity and immunoreactivity of antral extracts from man, pig and cat

1. The gastrin bioactivity and immunoreactivities of human, porcine and feline antral extracts were compared. 2. Human and porcine had similar activities but cat had much less. 3. The ratio of gastrin bioactivity to immunoreactivity was much greater with feline antral extracts than with human and porcine extracts.

Pancreotone, an inhibitor of pancreatic secretion in extracts of ileal and colonic mucosa

1. Pancreotone is a polypeptide material obtained from ileal and colonic mucosa by extraction with alcohol and subsequent precipitation by bile salts. 2. In anaesthetized cats in inhibits the actions of secretin on the pancreas, and of pancreozymin on the pancreas and gall-bladder. 3. Pancreotone has a less powerful inhibitory action on pentagastrin-stimulated gastric secretion. 4. The actions of pancreotone resemble the inhibitory effects on the pancreas and stomach of intraileal and intracolonic infusions of oleic acid and other substances in cats with the vagal and splanchnic nerves cut. Pancreotone may be the humoral mediator of these inhibitory effects. 5. A possible relationship between the actions of pancreotone and somatostatin on the stomach, and of pancreotone and pancreatic polypeptide on the pancreas, is discussed.

The development of a reliable and sensitive bioassay for gastrin in body fluids

The sensitivity and reliability of the Ghosh and Schild rat stomach preparation was improved by implantation of bulky intragastric cannulae, recirculation of the perfusate and measurement of conductivity instead of pH. With these procedures, the threshold values for gastrin I were in the range of 1-2 ng. In attempts to increase the sensitivity further it was shown that neither vagotomy nor antrectomy influenced the sensitivity of the method. The threshold values were not lowered by attempts to reduce gastrin metabolism through nephroligature or small bowel resection. Although rats fitted with portacaval shunts did raise the threshold, the limited increase in sensitivity was also achieved by selecting the rats that gave an initially high response to a test dose of gastrin thus avoiding the complicated shunt operation. The assay procedure enabled statistically valid measurements of gastrin in plasma and from tumour extracts from patients suffering from the Zollinger-Ellison Syndrome to be assayed using a 2 + 2 block design.

The half-life of exogenous gastrin in the circulation

1. A method of gastrin bio-assay is described which can be used on as little as 30 ng synthetic human gastrin I at a minimum concentration of 2.5 ng/ml.2. Pentagastrin or synthetic human gastrin I added to cat plasma can be stored on ice or at 4 degrees C, for periods up to 27 hr without apparent loss of gastrin activity.3. Between 1(1/2) and 13 min after the rapid I.V. injection of pentagastrin in the anaesthetized cat and between 1(1/2) and 15 min after the injection of synthetic human gastrin I, there is a rapid reduction of the gastrin concentration in the arterial plasma. The data relating log(10) gastrin concentration in arterial plasma with time can be fitted by a single term.4. Studies in vitro show that over the periods of time involved in the in vivo studies, both pentagastrin and synthetic human gastrin I are stable in cat plasma at 37 degrees C in concentrations which occurred in the circulating plasma.5. The half-life of pentagastrin in the circulating arterial plasma of the anaesthetized cat is 1.50 min (S.E. +/- 0.08) and the half-life of synthetic human gastrin I is 2.65 min (S.E. +/- 0.09).

Experiences with a rat bio-assay in the diagnosis of the Zollinger-Ellison syndrome

Reported here are the assay results, using the anaesthetized rat preparation of Lai (1964), of plasma from patients known or suspected to have peptide-secreting adenomata and these are compared with assays carried out on plasma from patients whose clinical history excluded such pathology. It is suggested that these demonstrate that this technique is of diagnostic value in this condition and that it has practical advantages over other bio-assay methods currently available and physiological advantages over immunological methods. It may well be that identification of the presence of tumour in these patients may first be made by immunological techniques to be followed by functional identification using a bioassay procedure such as is described here.