Inhibitory effect of sorbin on pepsin secretion in conscious cats and rabbits.

Sorbin, a 153 amino acid polypeptide isolated from porcine upper small intestine and its shortest synthetic derivative, the C-terminal heptapeptide (C7-sorbin), substituted by D alaninamide in the last position (D7-sorbin), have proabsorptive and antisecretory effect in the different parts of the intestine. We showed that labeled C7-sorbin accumulated not only in the enterocytes and the enteric nervous system but also in the gastric chief cells in the rat. The chief cell secretion of pepsin was then studied in two other species, the cat and the rabbit, simultaneously with the acid secretion of parietal cells. Lipase secretion was studied in the rabbit because lipase is exclusively secreted by the upper cells of the fundic glands, which do not secrete pepsin. The animals were equipped with a gastric fistula, fully innervated, and a Heidenhain pouch, vagally denervated, during a continuous perfusion of pentagastrin (PG) 2 microg/kg. h and vasoactive intestinal peptide (VIP) 4 microg/kg. h. D7-sorbin (100 pmol/kg. h) inhibited cat and rabbit pepsin secretion from the innervated gastric fistula secretion and from the cat denervated Heidenhain pouc secretion, but was without effect on acid secretion and lipase secretion. These data indicate that the inhibitory effect of sorbin is specific on chief cells because the acid parietal cell secretion in both species and lipase upper cell secretion of the fundic glands, in the rabbit, are not implicated.

[Gastric lipolysis in the young rabbit: origin and physiological importance of the lipase]. / Lipolyse gastrique chez le lapereau. Origine et importance physiologique de la lipase.

1. Lipolytic activity of pregastric and gastric secretions and extracts of the gastric wall of weaned and non weaned rabbit was measured in vitro on several substrates: lipids from rabbit and cow milk or from several lipid emulsions (triglycerides containing 3 identical chains, medium or long; coconut or sunflower oil; fats extracted from rabbit or cow milk). Only extracts and gastric secretions possess a lipolytic activity. This persists without attenuation if the pancreatic duct is ligatured. It is reduced after weaning. 2. This lipolytic activity evolves in the presence of high concentration of serum albumin (3%). In this case its optimal pH is 7. Its action preferentially liberates medium chain fatty acids, and, amongst long chain fatty acids, the unsaturated one. Sodium taurocholate (6 mM) slightly increases its effect, which remain unchanged after preincubation of gastric extracts or secretions at pH greater than 2.6. These results show that a gastric lipase exists in the young rabbit. 3. The differences observed between the conditions of activity of young rabbit gastric lipase, pregastric esterase or lipase of man, calf and rat and pancreatic lipase are discussed. We suggest the probable importance of gastric lipase in the particular way and means of digestion and absorption of the lipids of maternal milk in the young rabbit.

[Stimulation of insulin secretion by medium-chain fatty acids in the diet of young rabbits]. / Stimulation de la sécrétion insulinique par les acides gras à chaîne moyenne de l'alimentation chez le lapereau.

In the young rabbit, immunoreactive serum insulin (IRI) significantly rises during the first 5 min after suckling and then 20-60 min later, at which time the maximum level is reached. Blood glucose levels remain stable, blood ketone bodies increase 2.7 times and the liver glycogen levels decrease. Replacement of maternal milk by an equal volume of 0.9% NaCl, 2% lactose or 3.5% glycerol does not induce any change in IRI. IRI significantly rises if solutions of bovine milk proteins or skimmed rabbit's milk are administered. This effect is quickened and strengthened by the addition of coconut oil or lipids of rabbit's milk whereas sunflower oil is ineffective. It is suggested that medium-chain fatty acids, major components of rabbit's milk lipids, play an important role in the regulation of insulin secretion in the young rabbit.

[Gastrin, cholinergic and alimentary stimulation of gastric acid secretion in awake rabbits with a Heidenham pouch]. / Etude des stimulations gastrinique, cholinergique et alimentaire de la sécrétion gastrique acide d'une poche de Heidenhain chez le lapin éveillé.

Gastric acid secretion was studied in awake rabbits equipped with a Heidenhain pouch. The realisation of a pouch in the rabbit is reported for the first time. Post surgical complications were observed such as shocks, anaesthesia toxic effects, electrolytic impairments, skin burns and gastric ulcers. The continuous gastric secretion and the thinness of the muscularis are mainly responsible for the technical problems not observed in other species. Gastric acid secretion was high during basal periods in rabbits after 24 h of fasting with a collar to prevent any caecotrophia, which gives an empty stomach. It is equivalent to 20% of the acid output produced by pentagastrin (32 micrograms.kg-1.h-1). The highest acid output was obtained during carbaminoylcholine intravenous infusion (20 micrograms.kg-1.h-1) i.e. about twice that induced by pentagastrin. Regular dry diet did not produce any stimulation nor 2 DDG used as a control of complete vagal denervation of the pouch. Unlike in other species, gastric acid secretion of awake rabbit displays a preferential sensitivity to cholinergic stimulants and an insensitivity to regular diet which releases endogenous hormones humorally transmitted to the pouch. The use of rabbit isolated parietal cells or gastric glands to demonstrate the mechanisms of gastric acid secretion, makes it necessary to perform a complete physiological study of gastric secretion in the rabbit with the technique of the isolated pouch we describe here.

Effects of the stress of sampling and of anaesthesia on the metabolic status of suckling rabbits.

The stress of anaesthesia and of sampling on the concentrations of blood metabolites and tissue glycogen content was studied in awake, anaesthetized and decapitated young rabbits 1-2 days old ("young") and 17-18 days old ("old"), 24 h after the last controlled suckling. Stress of sampling and anaesthesia was particularly evidenced by high blood lactate observed for the three protocols in young rabbits and to a lesser extent in old animals. Decapitation appeared as the less aggressive procedure for blood lactate assessment in "young" and "old" rabbits. In "young" rabbits, blood glucose was not significantly modified by the mode of blood sampling while in "old" rabbits blood glucose was significantly lower in awake than in anaesthetized animals. Muscle and liver glycogen content data were not significantly different between the three protocols in old and young rabbits. From a comparison of these results with those found in adult animals in various species, it appears that blood puncture in awake "young" and "old" rabbits is a suitable procedure for determining the majority of blood metabolites except lactate in "young" animals.

[Tolerance and metabolic results of long-term administration of a mixture of saturated triglycerides by recto-colic route in rabbits]. / Tolérance et conséquences métaboliques résultant de l'administration chronique de mélange de triglycérides saturés par voie recto-colique chez le lapin.

Rabbit's and Dog's colonic absorption of triglycerides is shown in previous works. Further, we are studying the possibility to use the rectal route for nutritive substances. This way remains now poorly used and an exceptional therapeutic. However, bringing triglycerides in adequate state would be an energetic, supply, all the more as it is very difficult to provide potent caloric source in parenteral nutrition. This is why we investigate, on the Rabbit, the issues of chronic administration of glycerides by rectal route, on caloric balance and on a biochemical view to seek for in lipid composition of tissues the print of lipids administrated by transanal way. The animals are individually housed in metabolism units feeding a standard diet and drinking ad libitum. The treated subjects are given by transanal way, twice a day, for eight weeds, a sum of 1 g/kg of medium chain triglycerides. The metabolic balance-sheet is daily drawn. The clinic balance-sheet is set on the end, by biological controls to explore the hepatic and renal function (prothrombine ratio, transaminases (SGOT, SGPT), ornithine, carbamyl transferase (OCT), urea, total proteins ratio and electrolyte imbalance. We measure also the concentration of total lipids plasma and tissue (liver, kidney, heart, lungs, perirenal adipose tissue). The triglyceride composition and fatty acid composition of different lipids fractions of control and treated subjects are analyzed by gas-liquid chromatography. The animals support perfectly, without damage, a chronic and massive (1 g/kg/each day) administration of medium chain triglycerides by rectal route. The growth of treated subjects is normal. On the opposite, they adjust their alimentary consumption with the caloric charge of the diet, this is the reason why the reduction is about 12p. 100 with respect to the control animals. The coli-rectal administration of saturated glycerides produces at middle end only qualitative variations of lipids extracts. They essentially affect the triglyceride and fatty acid fraction of the tissue lipids, they become intermediate between that of control animals and the mixture administered by the transanal way. These results prove the integration of the glycerides in the metabolic pathway. They show the problem of the colonic absorption for the liposoluble substances. They authorize researches in view of a possible caloric assistance by this way.

Post-prandial lipase, pepsin and acid secretion of a Heidenhain pouch in the rabbit.

The kinetics of the gastric secretion of lipase, pepsin and acid were studied after a meal in Heidenhain-pouch rabbits. After a 24-h fast, feeding immediately stimulated (< 15 min) lipase (x 4.1) and later on pepsin (x 1.8) output which reached respectively 16 and 47% of the output observed after pentagastrin stimulation (64 micrograms.kg-1.h-1 for 1 h), and which were significantly correlated. Lipase concentration was enhanced earlier and to a greater degree (x 7.3) than pepsin concentration (x 2.5). No stimulation of high basal acid secretion occurred. It was concluded that: 1) gastric lipase secretion is stimulated by feeding in the rabbit; 2) pepsin secretion is stimulated by feeding. The modalities of the secretion of lipase and pepsin are compatible with the existence of distinct secretory cells; 3) acid secretion is not stimulated by feeding. The decrease in acid secretion during the post-prandial phase favors a physiological role for lipase which is altered by low pH. The absence of acid stimulation by feeding in the rabbit, in contrast to other species, requires additional studies on the release of gastrointestinal hormones, namely gastrin, cholecystokinin and somatostatin.

Evolution of glycogen and blood metabolites after controlled suckling at two periods of lactation in young rabbits.

In natural conditions young rabbit nurses once a day and therefore ingests the whole of his daily caloric intake during a single meal. The present work investigates glucose homeostasis during perinatal period in young rabbit by assessing blood glucose and glycogen stores before and after one single meal. Ponderal data, glycogen and blood metabolites were determined in 1-4 day- and 17-21 day-old rabbits before suckling and at different times (1, 3, 6, 9, 24, 48, 72 h) after controlled suckling. In "young" and "old" rabbits hepatic glycogen stores were exhausted after 48 and 72 h of fast. Within the first hours following milk ingestion, muscle and carcass glycogen did not vary until 9 h in the "young" and until 24 h in the "old" without notable variation of glycemia. From 24 to 72 h young rabbits were in a fasting period with low hepatic glycogen and a decrease of muscle and carcass glycogen, but glycaemia decreased only slightly at 48 and 72 h in "young" and at 72 h in "old" As blood alanine was decreased, it appears that gluconeogenesis was effective and that alanine-glucose and Cori cycles were operating in these conditions.

Cholinergic and pentagastrin stimulation of the gastric secretions of acid, pepsin and lipase in the awake rabbit.

Acid, pepsin and lipase secretions were simultaneously studied in awake rabbits with a Heidenhain pouch during cholinergic (carbamylcholine 20 micrograms.kg-1 x h-1) or maximal pentagastrin stimulation (64 mu.kg-1 x h-1). To avoid lipase inactivation by low pH, the pouch was perfused at a constant pH, with a solution irrigating the pouch without inducing any pressure. Acid and pepsin outputs were equally activated by both stimulants. Lipase output was stimulated much more by pentagastrin (x26) than by carbamylcholine (x6). The maximal lipase output preceded that of acid output. Lipase concentration increased in the gastric juice whereas pepsin concentration remained constant. A negative correlation was calculated between acid and lipase or pepsin and lipase output. A positive correlation was obtained between acid and pepsin. Our data show that pepsin and lipase secretions which come from distinct chief cells, in the rabbit, responded to the same stimulants but with quantitative and timing differences.

[In vitro study of the lipase activity of bacterial strains isolated from the rabbit cecum on C14-labeled triolein]. / Etude in vitro de l'activité lipasique de souches bactériennes isolées de caecum de lapins sur la trioléine marquée au 14C.

The lipase activity of bacterial species isolated from the caecum of conventional rabbits was studied by means of two groups of tests: (1) bacteriologic isolation and an identification of nine aerobic and anaerobic clones and (2) incubation of each of these clones in the appropriate medium in the presence of labelled triolein (oleyl 1-14C), a biochemical analysis of the radioactivity of the fractions obtained. The main results can be expressed in the following way: maximum hydrolysis of glycerides is achieved by two species: Bacillus licheniformis and Clostridium sporogenes. The reaction is proportional to the incubation time for incubations of less than 8 h. The release of fatty acids is concomitant to the synthesis of phospholipids and of fatty acid methyl esters.

Interaction between pepsin and acid secretion during fundic perfusion in cat and rabbit.

1. The effect of perfusion at pH 5.5 of a Heidenhain pouch on acid and pepsin secretion was studied in cats and rabbits. 2. In basal conditions, acid secretion was not modified by the perfusion while pepsin secretion was increased in both species. 3. After a meal, the perfusion did not modify the stimulation of acid secretion in cats nor the absence of secretions in rabbit. Stimulation of pepsin secretion was the same with or without perfusion in both species. 4. In rabbit, in contrast to cat, pepsin and acid secretions were independent during the meal-induced phase of gastric secretion.

Variation of gastric lipase secretion in the Heidenhain pouch of the cat.

In the cat, gastric lipase secretion was equally but weakly stimulated by pentagastrin, a major stimulant of acid secretion, and by carbamylcholine, a major stimulant of pepsin secretion. Lipase was also stimulated by fresh liver, which induces a large blood gastrin release and not by canned food, which is a poor gastrin releaser. Lipase output always preceded that of acid an pepsin. Lipase was not correlated with acid and pepsin secretion while acid and pepsin were well correlated during all stimulations but not in basal state. Lipase is co-localized with pepsin in the chief cells but is also present in pepsin-free cells, the mucus surface cells of the fundus and the antrum. The distribution of lipase explains the lack of correlation between pepsin and lipase as already mentioned. However, our data show that lipase secretion is under the control of gastric stimulants and might play a role in the gastric initiation of pancreatic meal lipolysis.