The 14C carbonate method for the direct measurement of the synthesis rates of liver-produced plasma proteins (McFarlane, 1963) is a valuable new tecnnique for the study of protein metabolism in gastrointestinal diseases. It is the purpose of this communication to describe a study in which this technique has been applied to investigate the mechanism of the hypoproteinaemia and disordered protein metabolism which occur in the stagant loop syndrome. METHODSSamples of fasting jejunal contents were obtained using the capsule designed by Shiner, Waters, and Gray (1963) and the samples were cultured both aerobically and anaerobically. Viable bacterial counts were made using serial dilutions (Miles, Misra, and Irwin, 1938). Urinary indicans were measured by the method of Curzon and Walsh (1962).The distribution ratio and fractional and absolute catabolic rates of albumin were determined by the method of graphical analysis (Matthews, 1957) using human serum albumin (Behringwerke) which had been labelled with 1251 by a modification of the iodine monochloride technique (McFarlane, 1958). Plasma volumes, used in calculating the intravascular pools of the plasma proteins, were measured using 131I albumin.Concentrations of the plasma aminoacids were estimated using a Technicon amino-acid AutoAnalyzer.Absolute synthesis rates of albumin and fibrinogen were measured simultaneously by a modification of the 14C carbonate method (McFarlane, 1963). Urea pool sizes and urea synthesis rates were calculated from the curve of clearance from the plasma and the urinary excretion of a known mass of 13C urea (63.5 atoms% excess), administered intravenously (Craigie, Jones, Rosenoer, and Smallwood, 1967). The 13C atoms%7, excess of urea in plasma and urine samples were determined by mass spectrometry in the
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.
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