The Effect of Changes in Antral pH on the Basal Release of Gastrin

Abstract

Acidification of the gastric antrum reduces the secretion from denervated and innervated fundic pouches in response to various stimuli (1-4). With sensitive radioimmunoassay technics it is possible to directly measure serum concentrations of gastrin released from the antrum during periods of variation in antral acidity (5). In the present work we report direct evidence on the timing of gastrin release after application of solutions at varying pH to antral mucosa which was not otherwise stimulated. Gastrin concentrations in blood draining the gastric antrum were measured by radioimmunoassay.Materials and Methods. Twelve adult mongrel dogs were divided into two groups of six. Each dog was fasted for 24 hr and anesthetized with pentobarbital sodium. At laparotomy the blood supply of the antrum was dissected to allow intermittent sampling of the antral venous outflow as described previously (6). The antrum was isolated from the fundus by means of a clamp placed across the antra-fundic junction. A doublelumen catheter for perfusion was placed via the duodenum into the antrum, and the pylorus was ligated around the catheter. During a 30 rnin basal period, the antral secretions were collected for determination of pH. Antral perfusion was then begun using solutions of 0.9% NaCl adjusted to pH vallues between 1.0 and 8.0. The rate of perfusion was 150 ml/hr; the inflow pressure was less than 2 cm H20 and visible distension of the pouch did not occur. Antral venous blood samples for gastrin measurement were obtained twice in the basal state (-15 min and zero time) and a t 15 min 1 Svpponted by grant AM 15241 from the National Institutes of Health and by a grant from The: John A. Hamtford Foundation, Inc. intervals throughout the experiments.I n six dogs (Group 1) continuous antral perfusion was begun a t pH 7.0, and every 30 min the pH of the perfusate was lowered by 1 unit in order to make the antrum more acid. In the other six dogs (Group 2) the antrum was perfiused for 30 min periods, first at pH 7.0, then serially a t pH 3.0, 8.0, 1.0 and 7.0. Sections of antral mucosa were taken for histologic study a t the end of each experiment. The gastrin concentrations in the serum of the antral venous blood were measured by radioimmunoassay ( 5 ) and are expressed as the mean of the observed values with the corresponding standard error (2 SE) . Student's t test was used to determine statistical significance of the data.Results. Irrigation of the antrum with solutions of varying acidity produced no histologic evidence of injury to antral mucosa.Group I (Fig. 1.) The results of measurement of gastrin values in antral venous blood in the six dogs are shown in Fig. 1. The mean basal serum gastrin was 172 t 23 pg/ml. The pH of the aspirated basal secretions from the antral pouch was between 3.5 and 5.0. Irrigation of the antrum with saline pH 7 increased the gastrin concentration to a peak of 390 t 69 pg/ml ( p < 0.02). Stepwise lowering of the pH of the antral perfusate resulted in progressive diminution in gastrin values. At pH 5 ...

Changes in Gastric Function and Healing of Chronic Gastric Ulcers in Aged Rats

“…In general, serum gastrin is known to increase under conditions of high intragastric pH (31). However, we found that the serum gastrin level did not increase in aged animals in spite of reduced gastric acid secretion, as compared with that in young animals.…”

ACTIVATION OF HISTIDINE DECARBOXYLASE BY H2‐RECEPTOR BLOCKADE: MECHANISM OF ACTION

“…The great majority of gastrin cells in the digestive tract of the rat are found in the antrum and in the regions immediately adjacent to the antrum (Larsson, Hakanson, Rehfeld, Stadil & Sundler, 1974 (Figure 2). Conceivably, the elevation of antral pH that results from the inhibition of acid secretion facilitates gastrin release (Becker, Reeder & Thompson, 1973). The H2-receptor antagonists may thus be added to the list of agents that non-specifically activate rat stomach histidine decarboxylase through an inhibitory effect on acid secretion.…”

Acid and pepsin secretion of separated gastric pouches during perfusion of antral pouches with cholinergic stimulating and blocking agents and lignocaine.

“…The reductions in resting secretion produced by local anaesthetic and blocking agents suggest that gastrin release is contributing to its maintenance even in the isolated double pouch preparation. Becker, Reeder & Thompson (1973) showed gastrin secretion from extrinsically denervated antral pouches when their contents were maintained at about neutral pH. In the present experiments the pH of the antral pouches before and during their perfusion may have favoured their secretion of gastrin, being pH 6-0-6-5 during saline perfusions and 6-8-8*6 when simply 224 ANTRAL CONTROL OF ACID SECRETION IN SHEEP 225 exposed to their own exocrine secretions (McLeay & Titchen, 1975).…”