In vitro inactivation of pancreatic enzymes in washings of the rat small intestine

Electrophoretic separation of proteolytic enzymes in pancreatic juice collected with the pouch or catheter method

CONCLUSION

The results of this study demonstrated that proteolytic enzymes in pancreatic juice from pigs prepared with the pouch method (PM) were nearly fully active or were fully active. When activation with enterokinase was carried out further inactivation and/or breakdown occurred for chymotrypsin C and cathodal trypsin. In addition, some inactivation and/or breakdown of proteolytic enzymes in pancreatic juice occurred during collection of pancreatic juice from PM pigs.

METHODS

Samples of pancreatic juice were collected from growing pigs using either the PM or the catheter method (CM). An isolated pouch was prepared where the pancreatic duct enters the duodenum, and three pigs were fitted with a pancreatic pouch re-entrant cannula. Three different pigs had a catheter surgically inserted into the pancreatic duct. Pooled 8-h samples of pancreatic juice were analyzed before and after activation with enterokinase. Chymotrypsin, trypsin, and elastase activities were identified in pancreatic juice after separation by electrophoresis in 1% agarose gels at pH 8.6 using N-acetyl-DL-phenylalanine-beta-naphthyl ester (Ac-Phe-beta ne) as a substrate.

RESULTS

This qualitative enzyme assay indicated that a considerable amount of chymotrypsin C, anodal trypsin, chymotrypsins A and B, elastase II, and cathodal trypsin were present in samples of nonactivated pancreatic juice from PM pigs. In contrast, the only active enzymes identified in pancreatic juice from CM pigs were very small amounts of chymotrypsin A and elastase II. The amounts of chymotrypsin C and cathodal trypsin were lower in activated than in nonactivated pancreatic juice from PM pigs. However, there were increases in the amounts of the other enzymes when pancreatic juice from PM pigs was activated. As expected, the activation of pancreatic juice from CM pigs resulted in the measurement of very high amounts of all the proteolytic enzymes. The amounts of anodal trypsin, chymotrypsins A and B, and elastase II were higher in activated pancreatic juice from CM pigs than from PM pigs.

Preparation and characterization of pancreatic lipase immobilized in Eudragit-matrix

Pancreatic lipase (EC 3.1.1.3) was immobilized by entrapping in a commercial preparation of acrylic/methacrylic acid ester-based copolymer (Eudragit E 30 D). The activity of the immobilized lipase beads with a diameter of 1.5-2.0 mm was found to be lower than that of the free lipase. The optimum pH was shifted to the alkaline region and the thermal stability increased, whereas the optimum temperature level remained unchanged. The most important reason for the decreased activity was diffusion limitations. The diffusion of the substrate and products became more pronounced, and lipolytic activity increased upon addition of n-hexane into the reaction medium. The storage and operational stabilities of the immobilized lipase were investigated, and both characteristics were found to be increased when compared to the free enzyme. Furthermore, mechanical or magnetic stirring during the operation were found to have no influence on the carrier-matrix as determined by nephelometric measurements.

Microorganisms associated with epithelial surfaces and stability of the indigenous gastrointestinal microflora

Indigenous microorganisms of many genera and species associate with mucosal epithelia in the gastrointestinal tracts of animals and humans. These mechanisms may involve a high degree of specificity for host and surface habitat. They may include a capacity of the microorganisms to adhere to the membranes of substratum epithelial cells, to colonize and utilize as a source of nutrients the mucus overlying epithelial cells, and to be motile and attracted into the mucous layer by chemotaxis. The microbes must be able as well to thrive in the nutritional and environmental conditions prevailing on the epithelial surfaces. Microbial communities associated with epithelial surfaces are critical for maintaining a microflora in areas of the tract (i.e., stomach, small intestine) where the lumenal content moves at a rate exceeding the maximum rates at which indigenous microorganisms can multiply. Such communities even may be important in areas (i.e., the cecum and colon) where the content moves at rates below those at which the microbes can multiply. In such areas, microorganisms colonizing mucus on the epithelium and in the crypts of Lieberkuhn may provide a stable inoculum for the lumenal content which may be altered in composition in times of dietary change. Microorganisms associated with gastric and intestinal surfaces undoubtedly serve in a major way to stabilize the composition of the indigenous gastrointestinal microflora. At the molecular level, however, little is known about the mechanisms stabilizing the composition or the biochemical and genetic activities of the microflora. Such mechanisms are important subjects for research in the future.

Measurement of bile acids in fasting gastric aspirates: an objective test for bile reflux after gastric surgery

We measured the concentration of bile acids in gastric aspirates from patients who had had operations for peptic ulcer. Some patients were asymptomatic and some had postoperative symptoms of the type that have been attributed to duodenogastric reflux. Samples were obtained via a nasogastric tube when the patients were fasting, after food, after pentagastrin, and overnight. We related the concentration and amount of bile acid and the volume aspirated to the presence or absence of symptoms and compared the results with radiological and endoscopic assessments of duodenogastric reflux. The most useful index to discriminate between symptomatic and asymptomatic patients was the amount of bile reflux in half an hour's aspiration from the fasting stomach; this we have termed 'fasting bile reflux' (FBR) and expressed as mumol bile acids refluxing/hour. A figure greater than 120 mumol/h was present in 17 of 22 symptomatic patients and in all who complained of bile regurgitation or bile vomiting. The FBR was less than 120 mumol/h in all of 20 asymptomatic patients, although some of them had reflux detected radiologically and endoscopically.

Lack of adaptation of pancreatic colipase in rats and mice

A new automated potentiometric method for the determination of colipase was developed, taking advantage of the reactivation of purified lipase, in the presence of bile salt and at pH 6.5. High-fat and high-starch diets induced an opposite regulation of lipase and amylase in the rat pancreas. At the same time, the level of colipase was not influenced by nutrition. During fasting and in alloxan diabetes, the specific activity of lipase almost doubled, that of amylase decreased sharply, and colipase was not affected in the rat pancreas. In obese-hyperglycemic mice, suffering from obesity, hyperinsulinism, and moderate diabetes, there was also no regulation of pancreatic colipase. Thus, at variance with a number of hydrolases, there was no dietary or hormonal adaptation of colipase. However, this was probably without any bearing on intraluminal lipolysis. Indeed, comparison of lipase and colipase activities in pancreas and in small intestine suggests that colipase concentration is not a limiting factor of intraluminal lipolysis. The molecular mechanism of this assumption is discussed on the basis of in vitro studies.

Concurrent studies on the flow of digesta in the duodenum and of exocrine pancreatic secretion of calves. The collection of the exocrine pancreatic secretion from a duodenal cannula

1. Two surgical techniques were developed in the calf to study the role of pancreatic secretion in digestion. The secretion was collected through a cannula placed in a small sac of duodenum into which the pancreatic duct drained. The continuity of the duodenum was re-established in the first technique by duodenal re-entrant cannulas, and in the second technique by end-to-end anastomosis of the duodenum with a cannula placed cranial to the anastomosis to return the pancreatic secretion. The accessory pancreatic duct was ligated.

2. The flows of digesta through the duodenum of milk-fed calves were 5505, 6369 and 7709 ml/12 h at 7, 24 and 63 d of age respectively, similar to values reported previously in the literature. In a 12 h collection period 297, 441 and 602 ml pancreatic fluid were secreted by calves of 7, 24 and 63 d of age respectively. The secretion from the mucosa of the duodenal sac was 40 ml/12 h in two other calves.

3. The rate of secretion from the pancreas varied markedly in milk-fed calves, being lowest 2–3 h and highest 6–10 h after feeding. Changes in the concentration of chloride and bicarbonate with pancreatic secretion rate were indicative of a secretin stimulus to secretion.

4. The rates of inactivation of pancreatic enzymes collected from the duodenal sac were measured at 4°, 20° and 39°.