The assay of urogastrone

Abstract

Ghosh (1958) reported a method for the assay of inhibitors of acid gastric secretion in the rat based upon the procedure for the continuous recording of gastric secretion described by Ghosh & Schild (1958). This method differed from earlier assay procedures in two main respects: (1) several doses of inhibitor were administered in succession so that each experiment comprised one or more assay blocks; (2) the inhibitory drug was given before the stimulant and was thus used to prevent rather than to counteract the effect of the latter.Whilst this method seemed satisfactory for the assay of atropine-like drugs, Ghosh (1959) found that in assaying the secretory-inhibitory activities of gonadotrophins and related urogastrone-like substances (Ghosh, 1956) it was most economical to administer only one dose of inhibitor to each rat because of the variability in the rate of recovery from inhibition in different rats. The object of the present work has been to modify the procedure for continuous recording of gastric-acid secretion to enable several doses of urogastrone to be given to each animal so as to benefit from the greater precision afforded by multiple doses. A method has been developed in which carbachol is used as the secretory stimulant and a block of four doses of urogastrone is administered to each rat. METHODSThe method for the continuous recording of acid gastric secretion in the urethanized rat maintained at 300C (Ghosh & Schild, 1958) was modified as follows. The operative technique was simplified to avoid any undue handling of the stomach. It was found that instead of opening the stomach simple washing by way of the oesophageal tube with 500 ml. tap water removed all food debris from the secreting portion of the stomach. Some food residues were left in the ruminal portion of the stomach but this did not seem to interfere with the assay.In previous work histamine was used as the secretory stimulant with dilute sodium hydroxide as the perfusing fluid. However, carbachol gave larger and more consistent acid responses and in addition these responses were readily inhibited by urogastrone. We have therefore adopted carbachol as the secretory stimulant, but in order to obtain a linear relation between the recorded pH and the increased acid secreted, we have replaced the dilute sodium hydroxide perfusion fluid with a phosphate-citrate buffer at pH 7x3: 'stock solution', citric acid 24 g+KH2P04 15-6 g made up to 1 1. with distilled water; working solution: 20 ml. stock solution + 8.1 ml. N-NaOH made up to 2 1. with distilled water.

Receptors Mediating Some Actions of Histamine

“…As the sensitivity of the rat stomach increases during the first two or three responses (Rosenoer & Schild, 1962) by Rosenoer & Schild (1962) Table 1 since it stimulated gastric acid secretion in the rat. In the cat, however, it was inactive when administered by slow intravenous infusion in doses up to ten times that effective with histamine.…”

The preparation of urogastrone

“…Urogastrone assays were carried out by a 2 + 2 or 2 + 1 procedure based upon a technique for the continuous perfusion of the stomach of the rat at 300 C (Ghosh & Schild 1958;Rosenoer & Schild, 1962). The pH of the effluent perfusate was measured by a continuousflow glass electrode and a recording pH meter.…”

The effect of atropine and metiamide on pepsin secretion of the rat

“…The rats were anaesthetized with urethane (1.2 g kg -~ i.p.) and prepared for the measurement of acid and pepsinogen secretion according to ROSENOR and SCHILD [7] with the following modification. In order to diminish the dead space in the stomach and to avoid any operative damage a small thin-rubber balloon was introduced through the esophagus into the stomach and placed under visual control in the non-secretory part (forestomach).…”