Physiological determination of release of secretin and pancreozymin from intestine of dogs with transplanted pancreas

L-amino acid sensing by the extracellular Ca2+-sensing receptor

The extracellular calcium (Ca(2+)(o))-sensing receptor (CaR) recognizes and responds to (i.e., "senses") Ca(2+)(o) as its principal physiological ligand. In the present studies, we document that the CaR is activated not only by extracellular calcium ions but also by amino acids, establishing its capacity to sense nutrients of two totally different classes. l-Amino acids, especially aromatic amino acids, including l-phenylalanine and l-tryptophan, stereoselectively mobilized Ca(2+) ions in the presence of the CaR agonists, Ca(2+)(o), gadolinium (Gd(3+)(o)), and spermine in fura-2-loaded human embryonic kidney (HEK-293) cells stably transfected with the human CaR. l-amino acid-dependent effects were observed above, but not below, a threshold level of Ca(2+)(o) of approximately 1.0 mM. l-Amino acids, particularly aromatic amino acids, also stereoselectively enhanced the sensitivity of the CaR to its agonists, Ca(2+)(o) and spermine. Branched-chain amino acids were almost inactive, and charged amino acids, including arginine and lysine, were much less effective than aromatic and other amino acids. l-amino acid mixtures emulating the amino acid composition of fasting human plasma reproduced the effects of high concentrations of individual l-amino acids on Ca(2+) mobilization and enhanced the sensitivity of the CaR to Ca(2+)(o). The data presented herein identify the CaR as a molecular target for aromatic and other l-amino acids. Thus, the CaR can integrate signals arising from distinct classes of nutrients: mineral ions and amino acids. The actions of l-amino acids on the CaR may provide explanations for several long recognized but poorly understood actions of dietary protein on calcium metabolism.

Response of rat exocrine pancreas to high-fat and high-carbohydrate diets

Intake of diets with high fat content is a risk factor for acute pancreatitis and pancreatic cancer. The underlying mechanisms leading to the development of these diseases due to high fat intake are currently unknown. The current study was designed in rats to determine the physiologic and pathological consequences of a highfat diet that contained excess amounts of cottonseed oil or a high-carbohydrate diet that contained high amounts of sucrose on the exocrine pancreas. Rats were maintained on the diets for 4 weeks, and a cannula was inserted into the right jugular vein and one into the pancreatic duct for collection of pancreatic juice. Volume of the pancreatic juice and concentrations of amylase, lipase, and trypsinogen in the pancreatic juice were measured before and after infusions of CCK-8. Results showed that basal and CCK-stimulated pancreatic outputs of volume, amylase and lipase but not trypsinogen, were significantly elevated in intact rats given a high-fat diet when compared with rats given a high-carbohydrate diet. Forty-eight hours later, rats were sacrificed, and parts of the pancreas were removed for isolation of pancreatic acinar cells and for histopathologic studies. Pancreatic acini isolated from rats on a high-fat diet showed significantly lower basal and CCK-stimulated amylase release when compared with those on a high-carbohydrate diet. Histology of the pancreas of rats on a high-carbohydrate diet appeared normal; however, the pancreas of rats on high-fat diet showed significant alterations in exocrine pancreas. These results showed abnormalities in the exocrine pancreas of rats on a high-fat diet, that were not found in rats on a high-carbohydrate diet; further, they support the contention that a high-fat diet has a deleterious effect on the pancreas.

The potency of dietary amino acids in elevating plasma cholecystokinin immunoreactivity in cats is related to amino acid hydrophobicity

Incomplete agreement exists on the relative potency of amino acids in stimulating endocrine secretion of cholecystokinin (CCK). Species and methodological variations have been suggested to account for the apparent inconsistencies. In the present research, the CCK-releasing potency of dietary amino acids was evaluated in cats using plasma CCK-like immunoreactivity (CCK-LI) as an indicator of CCK secretion rather than pancreatic protein and enzyme secretion, as has been used in past research. Oral-gastric administrations of a casein-simulating amino acid mixture increased (P < 0.05) plasma CCK-LI but not to the extent of that observed for casein or sodium oleate. The response in plasma CCK-LI to administrations of 50 mM solutions of amino acids was significant (P < 0.05) for tryptophan, phenylalanine, leucine, and isoleucine and the response increased linearly (P < 0.01) with increasing amino side-chain hydrophobicity. Control administrations of water and saline also evoked elevation in plasma CCK-LI, but the responses were so transient that amino acid effects were not obscured. This was substantiated by the finding of a significant linear (P < 0.001) dose response to phenylalanine administration. Cholecystokinin-8, 33 and 58 were among the CCK molecular forms identified by HPLC in plasma after administrations of phenylalanine and water. The present findings indicate that lipophilic amino acids released during digestion account for at least part of the endocrine CCK response in cats to ingested protein. The greater CCK-releasing potency observed for intact protein relative to free amino acids may have been the result of a slow digestive release of amino acids, elaboration of peptide secretogogues or protection of protease-sensitive releasing factors.

Role of secretin and cholecystokinin in oleic acid-stimulated pancreatic secretion in rats

We investigated the possible role of endogenous secretin and cholecystokinin (CCK) on oleic acid-stimulated pancreatic exocrine secretion in anesthetized rats. Intraduodenal infusion of oleic acid (pH 6.5) in three different doses (0.06, 0.25 and 1 mmole/hr) resulted in dose-related increases in pancreatic juice volume, bicarbonate and amylase outputs (r = 0.665, 0.736 and 0.517, respectively) (P less than 0.001). Plasma secretin and CCK concentrations also elevated significantly in response to oleic acid, in a dose-related manner (r = 0.721 and 0.546, respectively) (P less than 0.001). There were statistically significant correlations between plasma secretin concentrations and bicarbonate outputs, and between plasma CCK concentrations and amylase outputs in response to oleic acid (P less than 0.01). Potent CCK antagonist, CR 1409 (5 mg/kg.hr) administered intravenously suppressed completely increase in amylase output induced by oleic acid, and partially in juice volume and bicarbonate output. It is concluded that both endogenous secretin and CCK play important roles on oleic acid-induced pancreatic secretion in rats.

The influence of cutting the pancreatic nerve plexus on exocrine function in the pancreas of rats

This study was performed to clarify changes in protein synthesis and exocrine enzymes of the pancreas after cutting the pancreatic nerve plexus of Wistar rats. The rats were divided into two groups, consisting of a group that underwent cutting of the pancreatic nerve plexus (neurotomy group) and a group that underwent a sham operation (control group). 3H-leucine uptake in the pancreatic protein fraction of the neurotomy group at 3, 5 and 7 days after the operation was significantly lower than that of the control group (P less than 0.05-0.01), and this low uptake returned to the normal range at 14 days. Amylase, lipase and trypsin values in pancreatic tissue of the neurotomy group decreased during the period of from 1 to 7 days, and there were significant differences in the values of the respective enzymes at 5 or 7 days between the neurotomy and the control group (P less than 0.05). Thereafter, all enzyme values increased to within the normal range. Upon examination of pancreatic blood flow using a microsphere, the neurotomy group showed a significant reduction at 7 days compared with the control group (P less than 0.05), and thereafter exhibited recovery of blood flow. These results indicate that after cutting the pancreatic nerve plexus, exocrine function in the pancreas is reduced immediately but recovers within a short period of time, and that these changes in exocrine function are affected by blood flow in the pancreas.

Enteroinsular axis

A physiological role for GIP as an insulinotropic hormone involved in the enteroinsular axis has been established and ingestion of glucose, fatty acids and certain amino acids will produce an increase in circulating IR-GIP levels. The insulinotropic action of GIP is glucose concentration dependent in normal animals. A role for GIP in NIDDM is equivocal although several studies have demonstrated elevated serum levels. Animal models have indicated a disturbance of GIP receptor function associated with hyperinsulinaemia, i.e. lowering of the minimum glucose concentration at which GIP is insulinotropic.

Pancreatic secretory response to intestinal stimulants: a review

In humans and many laboratory animals, protein digestion products such as peptides and amino acids and fat digestion products such as fatty acids and monoglycerides are potent intestinal stimulants of pancreatic enzyme secretion. The pancreatic enzyme response to these intestinal stimulants is related to the perfused load (amount per unit time) rather than to concentration. Both neural and hormonal pathways mediate the enzyme response to these intestinal stimulants. Enteropancreatic, cholinergic, vago-vagal reflexes are probably the most important mediators of the enzyme response to low loads of amino acids and fatty acids; hormones, such as cholecystokinin, seem to be the major mediators of the response to high loads of amino acids and fatty acids. Under physiological conditions it is probably the interplay of neural and hormonal mechanisms which regulates the pancreatic response to these stimulants. Gastric acid is the major regulator of postprandial pancreatic bicarbonate secretion. Secretion released by HCl is probably the most important physiological hormonal mediator of postprandial pancreatic bicarbonate secretion; its effect being potentiated by extrinsic (vagal) and intrinsic (intrapancreatic) cholinergic nerves and release of other hormones, such as cholecystokinin.

Autoimmunity to pancreatic juice in Crohn's disease. Results of an autoantibody screening in patients with chronic inflammatory bowel disease

The sera of 59 patients with Crohn's disease (CD) and of 46 patients with ulcerative colitis (UC) were tested for autoantibodies (Aab) by indirect immunofluorescence with modern histochemical techniques using 19 different human tissues as antigenic substrates. Control collectives consisted of 19 patients with coeliac disease and of 100 healthy subjects. It was possible to demonstrate a specific marker for CD: Aab against exocrine pancreas (Pab) were present in 39% of the CD sera (UC 4%, coeliac disease 0%, healthy controls 3%). High Pab titres were only detectable in CD sera (29%). The CD-related autoantigen was demonstrated to be a component of normal pancreatic juice. Pab in CD were fundamentally different from those sometimes occurring in chronic and acute pancreatitis. It is suggested that CD is caused by autoimmune reactions against a component of pancreatic juice. Pab in CD correspond to Aab against intestinal goblet cells (Gab), which occurred exclusively in UC (28%). Pab and Gab, but obviously none of the other Aab investigated in this study, are of diagnostic value in chronic inflammatory bowel disease.

Neural pathways for the release of gastrin, cholecystokinin, and pancreatic polypeptide after a meal in dogs. Role of gastric and splanchnic nerves

We have measured gastrin, cholecystokinin (CCK), and pancreatic polypeptide (PP) release after a meal in normal dogs under basal conditions and during atropine infusion, and after various neural sections. Denervation of the gastric antrum (antral vagotomy) abolished the early part of the gastrin response to food. Truncal vagotomy, celiac ganglionectomy, and atropine reduced the early release of CCK, which occurred before the start of gastric emptying, suggesting that a neural, cholinergic mechanism may release CCK immediately after a meal. PP release was abolished by truncal vagotomy, and also by antral vagotomy. As no direct pathways are known between the antrum and the pancreas, this suggests either that antral afferents are essential for this response or that vagally mediated hormone release from the antrum mediates PP release.

Release of cholecystokinin and exocrine pancreatic secretion in response to an elemental diet in human subjects

We investigated in human volunteers the effects of an elemental diet (ED) containing amino acids on release of endogenous cholecystokinin (CCK) using a highly sensitive and specific radioimmunoassay of CCK and exocrine pancreatic secretion using a dye dilution technique with polyethylene glycol 4000 as a nonabsorbable marker. Intrajejunal administration of ED at three different infusion rates (12.5, 25, and 50 ml/30 min) resulted in a significant increase in plasma CCK concentration in a dose-related manner. Plasma concentrations of gastrin or secretin, however, did not change. Pancreatic secretion of protein, amylase, and bicarbonate also increased significantly. The change in pancreatic secretion of protein, amylase, and bicarbonate output paralleled that of the circulating CCK level but not that of plasma secretin. Thus, the dose of amino acid contained in ED recommended for clinical use can significantly stimulate the release of CCK from the upper small intestine, raising the plasma concentration of CCK. This level can evoke a significant increase in exocrine pancreatic secretion.

Secretin is released by digestive products of fat in dogs

We investigated the effect of fat or digestive products of fat on the release of endogenous secretin in 15 gastric fistula dogs with either pancreatic fistulas or duodenal fistulas. In 4 dogs with both gastric and duodenal cannulas, intraduodenal administration of corn oil (Lipomul) at a dose of 15 mmol resulted in a significant increase in plasma secretin concentration, whereas in another group of 4 dogs with complete pancreatic duct ligation, the same amount of triglyceride failed to increase the secretin concentration. When Lipomul incubated with pancreatic enzymes was administered in the duodenum, a marked increase in plasma secretin concentration occurred in the 4 dogs with pancreatic duct ligations. In the 7 dogs with chronic pancreatic fistulas, intraduodenal administration of Lipomul resulted in a significant increase in both plasma secretin concentration and pancreatic secretion of bicarbonate when the pancreatic juice was allowed to flow into the duodenum, whereas no increase in either the secretin concentration or bicarbonate output was apparent using the same amount of Lipomul when the pancreatic juice was diverted from the duodenum. In 4 of these 7 dogs so studied, intraduodenal administration of oleic acid emulsion, with pH adjusted to 5.0 in graded doses, resulted in a dose-related increase in the secretin concentration that paralleled pancreatic bicarbonate output. The increases in both secretin concentration and pancreatic bicarbonate secretion were completely abolished by intravenous infusion of a rabbit antisecretin serum in the 4 dogs. Thus we conclude that release of endogenous secretin plays an important role in the mechanism of exocrine pancreatic secretion stimulated by digestive products of fat in dogs.

Stimulation of bile-pancreatic zinc, protein and carboxypeptidase secretion in response to various proteins in the rat

The objective of this study was to determine the rate of bile-pancreatic secretion of zinc, protein and carboxypeptidase (CP) in response to three different dietary proteins, egg white (EW), soy protein isolate (SPI) and casein. The infusion of protein into the duodenum stimulated a significant increase in the secretion rate of zinc, protein and CP in bile-pancreatic juice. There was a high degree of correlation between the concentration of zinc and enzyme activity (CPA and CPB) in bile-pancreatic juice indicating that zinc in bile-pancreatic juice is associated with CP activity. The average secretion rate of zinc, protein and CP during the 1-h period after infusion of protein was significantly greater after SPI infusion than after casein. The bile-pancreatic secretion rate of protein, zinc and CPB in response to EW infusion was consistently intermediate between SPI and casein and did not differ statistically from either. Only CPA secretion rate was significantly greater after EW than after casein. Differences in protein digestibility appear to account for the greater pancreatic response to SPI, and this factor may be important in understanding the effect of protein source on zinc bioavailability.

Comparative study of the effects of equal amounts of fat, protein, and starch on plasma cholecystokinin in man

The effect of ingestion of 50 g fat, 50 g protein, and 50 g starch on plasma cholecystokinin (CCK) concentrations was studied in eight healthy volunteers. Plasma CCK concentrations were measured by radioimmunoassay with Bolton-Hunter-labelled CCK 33, CCK 33 standard, and antibody T204. Antibody T204 was directed to the sulphated tyrosine region of CCK. Ingestion of fat and protein induced significant increases in plasma CCK, whereas ingestion of starch did not significantly influence plasma CCK levels. Peak increments in plasma CCK after fat (4.8 +/- 0.9 pmol/l) and protein (3.4 +/- 0.5 pmol/l) were significantly greater than that after starch (0.9 +/- 0.3 pmol/l). Similarly, the integrated plasma CCK secretion after fat (213 +/- 49 pmol/l X 120 min) and after protein (178 +/- 53 pmol/l X 120 min) was significantly greater than that found after ingestion of starch (9 +/- 23 pmol/l X 120 min). It is concluded that, in contrast to starch, fat and protein are potent stimuli for the release of CCK.

Pancreatic secretory responses to intravenous hyperalimentation and intraduodenal elemental and full liquid diets

Intravenous hyperalimentation and enteral elemental diets have both been advocated for the nutritional support of patients with acute pancreatitis, pancreatic fistula, and proximal small bowel fistula. The exocrine pancreatic responses to these nutrients compared to one another and to full liquid diet have been inadequately studied. Therefore, pancreatic protein, volume, and bicarbonate responses to graded doses of (1) intravenous hyperalimentation, (2) intraduodenal elemental diet, and (3) intraduodenal full liquid diet were compared in duplicate experiments in five dogs with chronic pancreatic fistulas. Both intraduodenal elemental and full liquid diets caused comparable and significant dose-related increases in pancreatic protein, volume, and bicarbonate outputs over basal levels (p less than 0.05). In contrast, there was no stimulation of pancreatic secretion by intravenous hyperalimentation. It therefore appears that of the methods studied, only intravenous hyperalimentation can provide full nutritional support while maintaining the pancreas at rest.

Pancreatic exocrine response to parenteral nutrition

Animal experimental data concerning pancreatic exocrine secretory response to parenteral nutrition is contradictory. We have studied the pancreatic exocrine output in a patient with a pure pancreatic fistula. In this patient, parenteral nutrition with hypertonic glucose, amino acids and fat emulsion was not associated with increases in fistula volume or protein output. Enteral protein and fat in this patient caused rapid increases in both fistula volume and protein output. This study supports the use of parenteral nutrition as a means of maintaining the pancreas at rest.

The response of the pancreas of the anaesthetized cat to secretin before, during and after reversible vagal blockade

Cooling the cervical vagi of the anaesthetized splanchnectomized cat to 2 degrees C caused a 54.4 +/- 8.8% inhibition of pancreatic electrolyte secretion stimulated submaximally with pure secretin. On rewarming the vagi there was a prolonged increase in secretion rate over and above the control rate which existed before cooling. The increase lasted about 90 min. There were no changes in acid/base status due to interference of the lung inflation reflex which could account for the inhibition of secretion and the subsequent rebound. Cold block of the cervical vagi increased the transpancreatic electrical conductance, indicating that vasodilation had occurred and therefore eliminated a vasomotor cause for the inhibition. Electrolyte secretion was also inhibited by bilateral vagal section. Atropine only partially prevented the inhibitory response to vagal cooling. A cholinergic mechanism, therefore, accounted for some but not all of the response to vagal cooling. It is concluded that even in the fasted, anaesthetized animal vagal impulses facilitate the action of secretin on the pancreas. This facilitation is only partially cholinergic; the major part of the response is due to some non-cholinergic transmitter substance. Such a mechanism may be necessary to potentiate the action of the very small amounts of secretin which appear to be released during a meal.

Effects of porcine gastric fundic factor, somatostatin, substance P, glucagon, neurotensin, bombesin, VIP, motilin, and pentagastrin on jejunal glucose absorption in the rat

The effects of a porcine gastric fundic mucosal extract (molecular weight less than 10 000) has been compared with the effects of eight candidate gastrointestinal peptides on glucose absorption from the jejunum in a rat model. Bolus injection of the extract produced immediate and marked depression of glucose absorption. None of the candidate peptides tested produced this response, although somatostatin and substance P depressed absorption as a late phenomenon after 30 minutes. We conclude that the effects of the fundic extract are not reproduced by any of these candidate peptides. This strengthens the evidence for a novel gastrointestinal peptide, resident in fundic mucosa, which affects absorption from upper small bowel.

Bile acid and pancreatic trypsin outputs are parallel during intraduodenal infusion of essential amino acids

There is disagreement as to whether contraction of the gallbladder occurs simultaneously with secretion of pancreatic enzymes during food ingestion. One study that employed exogenous cholecystokinin (CCK) alone showed dissociation of total bile acids (TBA) and trypsin outputs, while another study that employed exogenous CCK plus secretin showed parallel outputs of TBA and trypsin. Since previous studies have suggested that intraduodenal infusion of essential amino acids (EAA) evokes pancreaticobiliary secretion similar to that observed with food ingestion, we infused increasing doses of EAA intraduodenally in 10 subjects with intact gallbladder and in 10 subjects with previous cholecystectomy and measured total bile acids and trypsin outputs serially. In subjects with intact gallbladder, increasing molar doses of EAA induced parallel increases of TBA and trypsin outputs. In subjects with previous cholecystectomy trypsin outputs during infusion of EAA were similar to subjects with intact gallbladder, but their TBA outputs remained constant during the entire infusion period. Serial concentrations of plasma secretin did not change during intraduodenal infusion of EAA. These observations suggest that the gallbladder empties bile in concert with secretion of pancreatic enzymes following food ingestion.

Influence of topical anesthetic, anticholinergic and ganglionic blocking agents on endogenous secretin release and pancreatic secretion in dogs

The role of parasympathetic including local nerve control on the release of endogenous secretin and pancreatic secretion was studied in four conscious dogs prepared with both Thomas duodenal and gastric fistulae. Plasma secretin levels and pancreatic response during intraduodenal infusion of hydrochloric acid (HCl, graded doses doubling every 30 minutes from 0.3 to 2.4 mEq/10 min) rose significantly in dose-related fashion. Either atropine or hexamethonium, when given intramuscularly, did not inhibit HCl-stimulated endogenous release of secretin, but significantly suppressed pancreatic water, bicarbonate and protein secretions. Oxethazaine, when infused with HCl, suppressed a rise in both plasma secretin concentration and pancreatic secretion. The results obtained led to the conclusion that endogenous release of secretin is not under parasympathetic nervous control, but stimulated directly by intestinal contents.

Hormonal mediation of rat heart lipoprotein lipase activity after fat feeding

The effect of acute fat feeding on the response of two fractions of lipoprotein lipase in heart was explored. In rats, previously fasted, lipoprotein lipase activity released into the perfusate by heparin increased approximately 50% 4 h after fat feeding. The lipase activity remaining in the heart tissue after heparin perfusion showed no significant difference. When rats maintained ad libitum were intubated with glucose 2 h before the fat dose, a relatively larger increase (5-10-fold) in the heparin-releasable lipase activity was observed. The capacity of these hearts to hydrolyze 14C-labeled chylomicrons was also increased 4-5-fold over the controls. Fat ingestion has been reported to elevated plasma corticosteroid levels in rats. When adrenalectomized rats were fed fat, no significant changes in the heparin-releasable lipase activity were observed Hydrocortisone and corticotropin treatment increased the heparin-releasable lipase activity to the same degree as observed with fat feeding. These data suggest that the increase in heart lipoprotein lipase activity following fat feeding is mediated via corticosteroids.

Studies of a gastric fundic mucosal factor which affects absorption from the antrum and jejunum in the rat

1. A rat bio-assay has been developed in which the tracer ion technetium 99 m (99mTc) was used to monitor absorption from both the antrum and the jejunum of the rat. 2. Evidence has been obtained for the release of a humoral substance from the rat gastric fundus after alkalinization of the mucosa at pH 8, and this fundic factor has been shown to reduce the absorption of the tracer ion 99mTc from both the lumen of the antrum and of the jejunum in the rat. 3. Intravenous infusion of a neutral extract of porcine fundic mucosa, distension of the rat fundus with air or exposure of the fundic mucosa to alkaline buffer all decreased absorption of the tracer ion virtually to the same extent from the lumen of the antrum (P less than 0.001) and to a lesser extent from the lumen of the jejunum (P less than 0.05). This effect does not appear to be due to histamine. 4. Preliminary biochemical data have indicted that the biological activity in the mucosal extract is protein in nature and has a molecular weight of less than 10,000.

Additional observations on cholecystokinin and the vasoactive intestinal polypeptide

During the isolation of cholecystokinin from natural sources, as well as during its bioassay, inactivation by oxidation can cause problems. We have attempted to reactivate oxidized CCK by reduction at room temperature with N-methylmercaptoacetamide, recently stated to be the reducing agent of choice for the reduction of methionine sulfoxide to methionine [22]. We have not yet been unequivocally successful in these attempts, but the results seem promising. In the case of oxidized VIP and of oxidized tetragastrin, reduction with N-methylmercaptoacetamide does seem to result in reconversion of the peptides to their preoxidation states, as evidenced by thin layer chromatography on silica gel. We have, together with A. Holmgren and A. Ehrnberg, made observations suggesting the presence in rate liver cytosol of an enzyme which catalyzes the reductive reactivation of oxidized CCK with reduced thioredoxin as the immediate hydrogen donor. In collaboration with A. Light, Purdue University, we have found that enterokinase cleaves 39-CCK and 33-CCk with release of 8-CCK and the tetrapeptide immediately preceding it in the peptide chain. The conversion of 39-CCK to 33-CCK by the action of dipeptidyl amino-peptidase I has been confirmed.

The effect of intravenous fat emulsions in patients with pancreatic fistula

Three patients with pancreatic fistulae were given parenteral 10% fat emulsion (Intralipid) to study the effect of intravenous fat on pancreatic fistula output. Each patient received nutritional support with isovolumetric, isonitrogenous, and isocaloric solutions containing either hypertonic dextrose and amino acids, or hypertonic dextrose, amino acids, and a fat emulsion. Measurements of fistula volume, fistula amylase, lipase, and chloride concentrations, and fistula trypsin activity were performed. The patients were studied for periods of 10 to 26 days. No significant increases in any of the above parameters were noted during the periods when the fat emulsions were infused. In one patient the fistula closed spontaneously. We conclude that intravenous fat emulsions may be used to provide nutritional support for patients with pancreatic fistula without increasing pancreatic juice volume or enzyme content.

Intestinal capillary blood flow during metabolic hyperemia

It has been postulated that local circulatory control mechanisms regulate the O2 flux to parenchymal cells by two vascular mechanisms: changes in blood flow that minimize capillary PO2 variations and changes in the density of the perfused capillary bed through which O2 extraction is regulated. To test this prediction, isolated loops of canine jejenum and ileum were perfused at either constant blood flow or constant pressure, and intraluminal glucose was used to increase metabolic rate. In the constant-flow series, glucose increased O2 extraction, O2 uptake, and rubidium extraction. Resistance fell when the metabolic rate was elevated. In the constant-pressure series, glucose increased blood flow, O2 extraction, O2 uptake, and capillary filtration coefficients. These results show that vascular resistance falls and that capillary density increases following an increase in oxygen demand. Thus, the glucose-stimulated gut loop seems to be a valid model of metabolic hyperemia, and its behavior would be difficult to reconcile with a purely myogenic theory of intestinal blood flow autoregulation.

Effect of vagotomy on gastrointestinal hormones

Different types of vagotomy have been widely used in the treatment of peptic ulcer disease. A close relationship between the vagus nerve and the release or action of gastrointestinal hormones is necessary for the optimal activation of the gastrointestinal tract. The serum concentrations of the antral hormone gastrin are elevated after all types of vagotomy. The postvagotomy hypergastrinemia is due to the change in pH in the antral lumen or the gastric motility changes, both of which may lead to a proliferation of G cells. The reduction in pancreatic secretion after vagotomy is not due to changes in intestinal hormone release, but may be caused by the interruption of a postulated enteropancreatic reflex. Postprandial GIP release and serum insulin levels are not affected by vagotomy, but basal GIP levels are increased after vagotomy. Postprandial pancreatic polypeptide release is nearly abolished by vagotomy, but seems to normalize in the later postoperative course. These findings may be important for the interpretation of pathophysiologic changes after vagotomy.