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Programmed expression of several matrix metalloproteinases is an important feature of cutaneous wound healing. To study whether this also applies to gastrointestinal ulcer healing, we used in situ hybridization with 35S-labeled probes to localize sites of collagenase, stromelysin-1, and matrilysin expression in 26 samples representing peptic ulcers, Crohn's disease, and ulcerative colitis. In contrast to skin wounds, collagenase mRNA was not detected in the surface epithelium bordering gastrointestinal ulcer areas. However, together with stromelysin-1 mRNA, it was abundantly expressed by the granulation tissue in all types of ulcers. Signal for matrilysin mRNA and protein was detected in the mucosal epithelium bordering the ulcerations but never in the ulcer stroma. The gut basement membrane was disrupted under the matrilysin-producing epithelial cells as assessed by immunostaining for laminin. Tissue inhibitor of metalloproteinases (TIMP-1) mRNA never co-localized with matrilysin-positive mucosal epithelial cells. These data indicate that matrilysin plays a significant role in epithelial remodelling occurring in gastrointestinal ulcerations whereas collagenase and stromelysin-1 are involved in the reparative processes in the ulcer bed.

Tryptase, a serine endoprotease, was determined in mucosal biopsies from fundus, corpus, antrum and corpus-fundus of the stomach and from the duodenum in 15 controls, 66 patients with duodenal ulcer, 22 with gastric ulcer and 9 with duodenitis. Intra- and inter-assay coefficients of variation ranged from 3.3% to 8.0% and from 3.5% to 8.6%, respectively. In controls, the highest values for tryptase were found in the fundus and progressively decreased in the corpus, antrum and duodenum. Analysis of variance of data from repeated measurements, performed in six subjects having multiple determinations, achieved statistical significance (F = 16.85, P less than 0.001). Data from the corpus-fundus area documented a significant difference among patient groups (F = 2.70, P less than 0.05). Patients with an active gastric ulcer had higher mean values when compared to controls and to patients with healed gastric ulcer. A similar trend was found in patients with active duodenal ulcer. Furthermore, corpus-fundus tryptase evaluated longitudinally in three patients with an active ulcer (point A) and after healing (point B), showed significant decrease from point A to point B. By contrast it remained elevated or showed only minor decrease in two patients with a persistent active ulcer.

Cysteamine and propionitrile cause severe duodenal ulcers with perforation within 24-48 h after a single injection in rats. These animal models were used to gain insight into the early, preulcerogenic biochemical changes in the duodenal mucosa. The results indicate that a single sc injection of cysteamine and propionitrile induced dose- and time-dependent decreases in the activity of phosphoprotein phosphatase (PPPase) in homogenate and particulate fractions of rat duodenal mucosa. The decrease in enzyme activity was detectable 4 h after the injection of the ulcerogens, it was maximal at 12 h, and hardly detectable at 24 h. No effect on the enzyme activity was found under in vitro conditions. PPPase activity in the liver was not influenced by either cysteamine or propionitrile. Furthermore, the toxic but nonulcerogenic derivative of cysteamine ethanolamine had no effect on PPPase in the duodenum. Thus, the effect of the duodenal ulcerogens on PPPase activity was indirect and organ specific, related only to the target organ (i.e., duodenal mucosa). The effect of the drugs was also selective at the level of mucosal cells: both duodenal ulcerogens depleted protein and alkaline phosphatase but not lysosomal acid phosphatase. The decrease of PPPase activity could be a general property of the duodenal ulcerogens since it is independent of their effect on endogenous somatostatin.

Pyruvate kinase activity in gastric mucosal supernatant preparations shows large responses to exogenous effectors. At pH 7.5, fructose 1,6-diphosphate can cause large stimulations in activity. Alanine inhibits the reaction but this effect is partially reversed by fructose 1,6-diphosphate. In the absence of these compounds, 4.0-5.0 mM phosphoenolpyruvate (PEP) is required to generate maximal activity in the assay system used. Electrophoresis reveals an isoenzyme pattern containing only one form of pyruvate kinase, an M isoenzyme, in both fundic and antral mucosa. The pyruvate kinase of gastric mucosa thus resembles the M-type enzymes of leucocytes and liver. Measurements of activity at both 1.0 mM PEP and 4.0--5.0 mM PEP, with and without additions of fructose 1,6-diphosphate, are recommended for the reliable estimation of pyruvate kinase activity in this tissue.

Procedures were developed for the determination of the activity of the microsomal enzyme 3-hydroxy-3-methylglutaryl CoA reductase (HMG CoA reductase, EC 1.1.1.34) in human liver. The enzyme assay could be carried out with as little as 20 mg of fresh liver tissue, thus making the method applicable to specimens obtained by percutaneous liver biopsy. Experiments were carried out to determine optimal assay conditions and to establish the identity and radiopurity of the reaction product formed from 3-(14)C-labeled 3-hydroxy-3-methylglutaryl CoA. The specific activity of the enzyme was measured in a number of patients with different disorders of lipid metabolism.

The activity of beta-glucuronidase was studied in the gastric aspirate from normal individuals, cases of duodenal ulcer with pyloric stenosis and carcinoma of the stomach. The optimum pH for the activity of this enzyme in the gastric aspirate is 4.0 to 5.5. Cimetidine, a H2-receptor antagonist, was administered orally to obtain the optimum pH for the enzyme activity, when the pH of the gastric aspirate was less than 4.0. It is observed that the enzyme activity in cases of carcinoma of the stomach is markedly elevated (p less than 0.01), when compared with other cases in this study. It is suggested that the elevated enzyme activity in the gastric aspirate could be used as a biochemical marker in the diagnosis of carcinoma of the stomach.