Pepsin secretion in man after Histalog stimulation

Human gastric juice shows three separable pepsin fractions on chromatography on DEAE-cellulose. The response of these fractions to stimulation with beta-aminoethylpyrazole hydrochloride (Histalog) was studied. After a single intramuscular injection of Histalog (1.7 mg/kg body weight) there was an increase in the output of all three chromatographically distinguishable pepsin fractions. Little change was observed in the relative proportions of these three fractions and there was no evidence of selective stimulation of any individual fraction.

The pepsins from human gastric mucosal extracts

1. The pepsins and pepsinogens of the gastric mucosal extracts of two normal subjects, of seven patients with gastric adenocarcinoma and of two patients with duodenal ulcer have been investigated by agar-gel electrophoresis and by ion-exchange chromatography. 2. Of the eight zones of proteolytic activity that have previously been reported in normal human gastric juice, seven can be detected in activated fundic mucosal extracts. Of these seven, four can be attributed to discrete pepsins, numbered 1, 3a, 3 and 5. 3. Zone 7 results from the activity of one or more enzymes that are alkali-stable and are best referred to as gastric proteinases rather than as pepsins. Zone 7 is much more evident in mucosal extracts than in gastric juice. 4. Zones 4 and 6 may result respectively from the activity of a pepsin-inhibitor complex and of an unactivated zymogen. 5. It was not possible, by the chromatographic methods employed, to separate satisfactorily the individual pepsins from activated extracts or their precursors from unactivated extracts, so that the ascribing of a pepsin to a specific zymogen must be considered tentative. Even so, pepsin 3 appears to arise from at least two major precursors, if not from three, whereas pepsins 1 and 5 each arise from a single major precursor. 6. Pyloric mucosal extracts contain principally zone 5 but also zones 6 and 7. These zones in general behave similarly to the corresponding zones of fundic extracts, but pyloric pepsin 5 migrates slightly faster on agar-gel electrophoresis than does fundic pepsin 5 and is a different enzyme. Zones 1 to 4 are absent.

The pepsins of normal human gastric juice

1. The frequency of occurrence, under defined conditions, of the different human pepsins in the gastric juices of 50 normal subjects was investigated by agar-gel electrophoresis. 2. From a total of eight proteolytic zones located in the zymograms, no significant differences of occurrence existed between the sexes, or between subjects with or without gastric symptoms. 3. Two zones, numbered 3 and 5, occurred in all normal gastric juices. Zone 3 always exhibited the greatest proteolytic activity, then zone 5. The remaining enzymic zones were less well-marked and occurred less frequently. 4. A minor zone, 3a, was demonstrated within zone 3. The corresponding pepsin, 3a, has a mobility towards the anode 6-7% greater than has pepsin 3. 5. Of the eight zones, 1,2,3,3a and 5, at least, represent unique pepsins.

Peptic inhibition by macroanions

Heparin, dextran sulphate, dextran phosphate, chondroitin sulphate and degraded Λ-carrageenan inhibit peptic activity by substrate occlusion or depletion. This holds for various substrates and enzyme preparations, but the amount of inhibition observed varies with method and inhibitor used. The most active inhibitors of the series are disulphated on at least alternate sugar residues and in addition to disulphation high molecular weight confers, in certain conditions, greatest activity. High and low molecular weight macroanions have different inhibition characteristics and it is concluded that activity may depend upon the structure of the substrate-inhibitor complexes formed. Inhibition is not observed when substrate-inhibitor interaction does not occur, as when pepsin or N-acetyl-L-phenylalanine-L-diiodotyrosine (APDT) are used as substrate.