Postprandial levels of prolactin and gut hormones in breast cancer patients: association with stage of disease, but not dietary fat

Previous studies of the relationship between dietary fat and breast cancer have produced conflicting results and have provided no definitive evidence of a mechanistic link between fat and breast tumorigenesis. We conducted a study to compare postprandial levels of prolactin (Prl), a hormone suspected of promoting the growth of some human breast cancer, and several gut hormones, i.e., gastrin (Gs), vasoactive intestinal polypeptide (VIP), neurotensin (Nt), and cholecystokinin (CCK), following high- and low-fat isocaloric test meals. Data were obtained in the posttreatment period from 13 patients with breast cancer (nine stage I and four stage II), who were disease free clinically, and nine healthy controls. Subjects admitted to the research unit on 2 days were given the high-fat meal on day 1 and the low-fat meal on day 2. Blood samples were drawn before (i.e., fasting) and after test meal consumption. All hormone analyses were performed by radioimmunoassay. Results indicated a significant rise in postprandial Prl levels for stage II patients, but not for stage I patients or the controls. Postprandial Gs levels were also elevated, whereas VIP levels were markedly reduced in patients versus controls; these differences were most marked in stage II patients. No significant intergroup differences were noted in postprandial levels of Nt and CCK. Hormone levels of patients and controls did not differ between the test meal situations, which indicated that some other component of the test meals might have been responsible for altered Prl and Gs levels. The differences observed between the stage I and II patients indicated that diet may influence the aggressiveness of tumor behavior and development through alterations in postprandial hormone release.

An epidemiologic study of inflammatory bowel disease in Rochester, New York. Hospital incidence

The epidemiological understanding of inflammatory bowel disease has been limited by the referral bases of most inflammatory bowel disease studies. The Colitis-Ileitis Study Group of Rochester, N.Y., developed a community-wide, computerized cumulative registry of all inflammatory bowel disease patients hospitalized at the 8 community hospitals for 1973-86. Clinical data were abstracted from each of the 1651 identified hospital charts. All of these patients resided in Monroe County (city and suburbs) and the 5 contiguous counties (Genesee/Finger Lakes Region, population 1,030,640). Of the 1651 hospital patients identified in the study, 1358 resided in Monroe County (Rochester and its immediate suburbs, population 702,238). Incidence, defined as time of onset of symptoms of inflammatory bowel disease, rose from baseline rates in the 1930s to peak in 1980 (Crohn's disease = 50.29/10(5) per decade, ulcerative colitis = 35.12/10(5) per decade) and declined through 1986. For Crohn's disease, the age-specific incidence rates peaked in the 20-29-yr-old group in each of the 5 decades studied. Ulcerative colitis seems to occur at all ages and may have a bimodal distribution. There was a period effect, with the 1970s having the highest incidence of Crohn's disease and ulcerative colitis for each age group. However, the age-specific incidence rate for Crohn's disease showed a 40% decrease in the 1980s compared with the 1970s in the 10-39-yr-old group (p less than 0.001). The age-specific incidence rate for ulcerative colitis showed a 50% decrease in the 1980s compared with the 1970s in the 10-49-yr-old group (p less than 0.001).

Role of endogenous cholecystokinin on vagally stimulated pancreatic secretion in dogs

Pancreatic exocrine secretion was evoked by electrical stimulation of the vagus nerves (EVS) in dogs to determine whether a gut hormone was responsible for the pancreatic stimulatory activity. In 39 dogs, pancreatic juice was continuously collected to measure volume, bicarbonate, and amylase output, while portal and femoral venous plasma concentrations of gastrin, cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP), and pancreatic polypeptide (PP) were determined by radioimmunoassay. EVS produced a significant increase in the pancreatic secretion. Although concentrations of all four peptides significantly increased in plasma, only CCK at the concentration in venous circulation was bioactive in dispersed rat pancreatic acini preparations. This bioactivity of CCK was completely blocked by CR 1409, a CCK-receptor antagonist. The pancreatic secretion by EVS was reduced significantly by intravenous MK-329 (formerly L364,718) to as low as 22% of control values and was completely suppressed by intravenous atropine. The increment in plasma CCK by EVS was also significantly suppressed by atropine. The present study indicates that increased pancreatic secretion by EVS is in part mediated by endogenous CCK.

Ulcerogenic tumor syndrome of the pancreas associated with a nongastrin acid secretagogue

Among 30 patients with islet cell neoplasms or hyperplasia who exhibited marked gastric acid hypersecretion and peptic ulceration and/or diarrhea, fasting plasma gastrin concentrations were less than 150 pg/ml in 11 patients, whereas the remaining 19 patients had hypergastrinemia. Plasma extracts from seven of these 11 patients were assayed for acid secretagogue activity in rats. All seven plasma extracts had secretagogue activity that was not found in the plasma extracts of ten patients with ordinary duodenal ulcer disease. Each of the tumor or pancreatic tissue extracts obtained from nine patients exhibited secretagogue activity in rats even though tissue gastrin content was 101.9 pmol (213.8 ng).g-1 or less. The secretagogue activity of the tumor extracts was confirmed in conscious gastric fistula dogs. The tumors' secretagogue activity, in contrast to gastrin, was destroyed by trypsin. It was eluted between porcine motilin and human gastrin I from a Sephadex G-50 (Pharmacia LKB Biotechnology, Inc., Piscataway, NJ) superfine column and was not retained by CM-cellulose, at pH 8.5. Its retention time during reverse phase HPLC on a C18 column also differed from those of G17 and G34. Thus, this secretagogue activity appeared mediated by a small, acidic peptide with a molecular size of about 2000 to 3000 daltons. The present study indicates that plasma and tumor extracts of these 11 patients contain a gastric acid secretagogue activity mediated by a nongastrin peptide. We suggest that what may be a distinct clinical entity associated with endocrine neoplasms of the pancreas should be considered in the face of excessive acid hypersecretion without fasting hypergastrinemia.

Plasma secretin, CCK, and pancreatic secretion in response to dietary fat in the rat

The role of fat in regulation of pancreatic secretion was studied in conscious rats by measuring pancreatic secretion and plasma cholecystokinin (CCK) and secretin responses to intraluminal infusion of fat, protein, or trypsin inhibitor via the duodenum. In rats with pancreatic juice continuously returned to the intestine, intraduodenal infusion of 20% emulsified fat (Liposyn), 10% casein, and 0.4% ovomucoid trypsin inhibitor (OMTI) stimulated equivalent increases of approximately threefold in pancreatic protein output. Proglumide reduced fat-stimulated pancreatic protein secretion by greater than 90% but did not inhibit the response to OMTI. Fat significantly increased plasma CCK from basal levels of 0.5 pM to 2-3 pM, but it was a weaker stimulant of CCK secretion than casein (peak CCK levels greater than 10 pM) or OMTI (peak CCK levels 5-6 pM). Fat significantly stimulated secretin release (21.7 pM) compared with casein (6.8 pM), OMTI (4.4 pM), and NaCl (3.5 pM). The inhibition of fat-stimulated pancreatic secretion by proglumide indicates that the small amounts of CCK released by fat are necessary for a normal pancreatic response, suggesting that this response may be the result of potentiation between secretin and small amounts of CCK.

Effect of pancreatic juice and trypsin on oleic acid-stimulated pancreatic secretion and plasma secretin in dogs

We have investigated a negative feedback mechanism in the intestinal phase of pancreatic exocrine secretion in dogs with gastric cannulas and Thomas duodenal cannulas in whom pancreatic juice was collected by cannulation of the main pancreatic duct. Intraduodenal infusion of oleic acid emulsion in a dose of 18 mmol/h resulted in a significant increase in pancreatic secretion of water, bicarbonate, and protein, which was accompanied by increased plasma concentrations of both secretin and cholecystokinin. Infusion of pancreatic juice or bovine trypsin into the duodenum significantly inhibited the oleic acid-stimulated pancreatic secretion. This inhibition coincided with a significant decrease in plasma secretin level, whereas plasma cholecystokinin concentration was not affected by either pancreatic juice or trypsin. Neither pancreatic secretion nor plasma secretin concentration was affected by intraduodenal administration of NaHCO3 solution. The trypsin-induced suppression of pancreatic secretion was prevented by intravenous administration of secretin in a dose that achieved a plasma secretin level comparable to that during the oleic acid administration. This study indicates that a negative feedback mechanism is operative in the intestinal phase of pancreatic exocrine secretion in dogs, and endogenous secretin plays a significant role in the mechanism.

Effect of pancreatic juice diversion on secretin release in rats

We investigated a possible role of secretin in the mechanism of exocrine pancreatic secretion after exclusion of pancreatic juice from the intestine in anesthetized rats. Diversion of pancreatic juice from the duodenum resulted in a significant increase in plasma secretin concentration from 0.76 +/- 0.39 pM at 0 time to 3.09 +/- 0.30 pM at 4 h after diversion. This increase in secretin coincided with a steady but significant increase in pancreatic secretion of volume and bicarbonate. Intraduodenal administration of fresh pancreatic juice completely reversed the diversion-induced increases in both plasma secretin and pancreatic secretion. Intravenous injection of a rabbit-antisecretin serum blocked the increase of pancreatic secretion during diversion of pancreatic juice from the duodenum. Thus, we conclude that endogenous secretin is involved in a hormonal mechanism regulating increased pancreatic exocrine secretion in pancreatic juice-diverted rats.

Role of pancreatic polypeptide in the regulation of pancreatic exocrine secretion in dogs

The effect of intravenous infusion of synthetic human pancreatic polypeptide (HPP) or a rabbit anti-PP serum on pancreatic exocrine secretion was studied in 10 dogs with gastric and Thomas duodenal cannulas. The infusion of HPP, at a dose of 1 microgram.kg-1.h-1, achieved a plasma PP concentration that mimicked the peak plasma concentration of PP in both interdigestive and postprandial states. This dose of HPP significantly inhibited pancreatic secretion in the interdigestive state. By contrast, immunoneutralization of circulating PP by a rabbit anti-PP serum resulted in significant increases (P less than 0.05) in both interdigestive and postprandial pancreatic secretion, including water, bicarbonate, and protein. The increase in the pancreatic secretion paralleled a decrease in circulating PP level, which lasted for as long as 5 days. Furthermore, the anti-PP serum blocked the inhibitory action of exogenous HPP on pancreatic exocrine secretion. The present study indicates that endogenous PP plays a significant role in the regulation of the pancreatic exocrine secretion in both interdigestive and digestive states. Thus we conclude that PP is another hormone regulating pancreatic exocrine secretion in dogs.

Acid-independent release of secretin and cholecystokinin by intraduodenal infusion of fat in humans

In order to clarify a possible role of fat content in the release of secretin and cholecystokinin by liquid nutritional supplements in humans, duodenal pH and plasma concentrations of secretin and cholecystokinin were studied during the intraduodenal infusion of Ensure, Vivonex, 10% Intralipid, and sodium oleate. Significant release of secretin was observed with Intralipid and sodium oleate, while significant release of cholecystokinin was observed with all four testing solutions. Duodenal pH was rarely below 4.5 during the infusion of Ensure, Intralipid, and sodium oleate. Duodenal pH was high, greater than 6.0, when plasma secretin and cholecystokinin levels were elevated during the administration of Ensure, Intralipid, and sodium oleate. We conclude that both secretin and cholecystokinin are released in response to fat solutions in the duodenum and that low duodenal pH was not responsible for either secretin or cholecystokinin release during intraduodenal infusions of Ensure, Intralipid, or sodium oleate.

Role of pancreatic enzymes on release of cholecystokinin-pancreozymin in response to fat

In dogs prepared with either pancreatic duct ligation (PDL) or chronic pancreatic fistula (PF), we investigated the effect of pancreatic enzymes on release of cholecystokinin (CCK) in response to corn oil in the upper small intestine. In control dogs without PDL, intraduodenal administration of corn oil (Lipomul containing 15 mmol of triglyceride) resulted in a marked and sharp increase in plasma CCK concentration during the 1st h, which then decreased during the following 1.5 h. In PDL dogs, on the other hand, no immediate increase occurred during the 1st 45 min after which a modest but gradual increase occurred in plasma CCK concentration during the following 2 h. Likewise, plasma CCK concentration increased significantly when Lipomul predigested with pancreatic enzymes or oleic acid was administered to PDL dogs. The increase was comparable to the response to Lipomul alone in control dogs. The infusion of Lipomul resulted in similar responses of plasma CCK in PF dogs as were found in PDL dogs when pancreatic juice was diverted to the exterior from the duodenum. The increases in plasma CCK paralleled the pancreatic protein secretion, and a significant correlation was found between plasma CCK concentration and the protein output. The present observations indicate that release of endogenous CCK by fat from the upper small intestine depends on an adequate digestion of neutral fat by pancreatic enzymes. Thus pancreatic enzymes play an important role on release of CCK in response to a neutral fat.

Effects of SMS 201-995, a somatostatin analogue, on the exocrine pancreatic secretion and gut hormone release in dogs

The effect of SMS 201-995, an analogue of somatostatin, on pancreatic exocrine secretion was investigated in both interdigestive and digestive states in dogs. In four dogs with gastric and Thomas duodenal cannulas, the pancreatic juice was collected by direct cannulation of the main pancreatic duct. SMS 201-995 was infused intravenously at doses of 0, 15, 30, 60, and 120 ng/kg/hr for 2 to 3 hours in the following experimental conditions: (1) interdigestive pancreatic secretion, (2) pancreatic secretion stimulated by the intravenous infusion of both secretin, 0.06 CU/kg/hr, and cholecystokinin octapeptide (CCK8), 0.03 microgram/kg/hr, and (3) pancreatic secretion after ingestion of a test meal. Pancreatic juice was analyzed for volume and outputs of bicarbonate and protein. Plasma levels of motilin, pancreatic polypeptide (PP), CCK, and secretin were determined by radioimmunoassay. SMS 201-995 inhibited significantly the pancreatic secretion and release of hormones, including secretin, CCK, PP, and motilin, in all three experimental conditions. The inhibitory action of SMS 201-995 on pancreatic secretion and hormone releases was dose dependent.

Effect of cisplatin on myoelectric activity of the stomach and small intestine in dogs

The effect of cisplatin on interdigestive myoelectric activity (IDMA) of the gastric antrum, duodenum and jejunum, plasma concentration of motilin, and animal behavior was studied in seven conscious dogs with gastric cannulas and platinum electrodes implanted on the serosal surface of antrum and upper small intestine. Cisplatin given intravenously in a dose of 2 mg/kg resulted in complete interruption of IDMA and produced predominantly phase II-like activity, lasting as long as 24 hr. Six of the seven dogs exhibited retropropagation of spike bursts from the jejunum to the antrum which was accompanied by emesis. Retropropagation of spike bursts did not occur in one dog who did not exhibit emesis. In addition, abnormal spike bursts occurred frequently, including simultaneously occurring spike bursts in both duodenum and jejunum and nonpropagating short spike bursts in isolated segments of the upper small intestine. As phase III of IDMA disappeared, plasma motilin concentrations remained comparable to those in phase II of normal IDMA but without the cyclic increases. These studies indicate that cisplatin interrupts the regular cycle of IDMA as well as the plasma motilin cycle and produces retropropagation of spike bursts and abnormal spike bursts. These changes in both motility and plasma motilin levels may play a part in the mechanism of emesis induced by cisplatin in dogs.

Atropine abolishes the potentiation effect of secretin and cholecystokinin-octapeptide on exocrine pancreatic secretion in humans

Potentiating action between secretin and cholecystokinin on exocrine pancreatic secretion of bicarbonate has been well recognized. In the present study, we studied the effect of atropine on potentiating action on pancreatic exocrine secretion stimulated by exogenous secretin in physiologic dose and cholecystokinin-octapeptide in humans. Using a dye-dilution technique and a duodenal triple-lumen tube, pancreatic secretion of both bicarbonate and trypsin was determined while gastric juice was completely aspirated. Secretin given i.v. in a dose of 2.7 pmol/kg/h, which was known to achieve a similar plasma concentration of secretin after meal in humans, and cholecystokinin-octapeptide 26.2 pmol/kg/h potentiated pancreatic secretion of bicarbonate but not the pancreatic trypsin output. Atropine given i.v. in a dose of 1 mg/h abolished the potentiation effect of the two hormones on pancreatic bicarbonate output. Since the inhibitory effect of atropine on the secretin-stimulated bicarbonate output was statistically significant, the major inhibitory effect of atropine on the potentiation of pancreatic bicarbonate secretion appears to be its effect on the action of secretin.

Secretin is an enterogastrone in humans

We studied in humans the effect of exogenous secretin in a physiological dose on gastric acid secretion stimulated by pentagastrin and postprandial plasma gastrin concentration. Two doses of pentagastrin, 80 and 160 pmol/kg/hr were used to stimulate gastric acid secretion. Secretin in two doses, 2.8 and 5.6 pmol/kg/hr were tried to study the response on stimulated gastric acid secretion. Intravenous secretin in a dose of 5.6 pmol/kg/hr significantly inhibited the gastric acid output stimulated by intravenous pentagastrin in a dose of 160 pmol/kg/hr, from 11.25 +/- 1.5 to 5.99 +/- 1.34 meq/hr while lower dose of intravenous secretin (2.8 pmol/kg/hr) failed to inhibit the gastric acid output stimulated by the same dose of pentagastrin. However, the lower dose of intravenous secretin (2.8 pmol/kg/hr) inhibited the gastric acid output significantly from 8.78 +/- 1.21 to 6.37 +/- 1.62 meq/hr when gastric secretion was stimulated by the lower dose of pentagastrin (80 pmol/kg/hr). The plasma concentrations of secretin during intravenous secretin in a dose of 2.8 pmol/kg/hr was similar to postprandial plasma concentrations of secretin as previously reported. Doubling the dose of intravenous secretin resulted in almost twofold higher plasma concentrations than postprandial plasma concentrations. In addition, the low dose of secretin (2.8 pmol/kg/hr) suppressed the integrated postprandial gastrin response from 13.9 +/- 3.7 to 11.2 +/- 2.8 ng/min/ml (P = 0.05) when endogenous release of secretin was blocked by intravenous cimetidine. Since the dose of pentagastrin and secretin employed in this study fell in a physiologic range, the inhibitory effect of secretin on stimulated gastric acid secretion appears to be a physiologic action in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

A hormonal mechanism for the interdigestive pancreatic secretion in dogs

We investigated a hormonal mechanism involved with cyclic pancreatic secretion in interdigestive state in four dogs prepared with gastric and modified Herrera's pancreatic cannulas and four dogs prepared with gastric and Thomas' duodenal cannulas. Cholecystokinin-pancreozymin (CCK-PZ), secretin, pancreatic polypeptide (PP), and motilin were considered as candidate hormones that might be involved in the mechanism. Radioimmunoassays of the four hormones in serial plasma samples showed cyclic increases in only two hormones including motilin and PP, which coincided with the cyclic increase in pancreatic secretion. However, only motilin given intravenously produced a cyclic pancreatic secretion similar to spontaneous cyclic pancreatic secretion in interdigestive state. Although the magnitude of peak pancreatic secretion was not altered during intravenous infusion of motilin in doses of 0.06 microgram X kg-1 X h-1 or 0.06 microgram/kg, the peak secretion occurred more frequently than that during the control interdigestive state. Atropine administered intravenously abolished the cyclic increases in both plasma motilin concentration and pancreatic secretion. Exogenous secretin, CCK-PZ8 and PP failed to produce cyclic pancreatic secretion. To further elucidate the mechanism involved, the effect of intravenous infusion of a rabbit anti-CCK-PZ or antimotilin serum on the cyclic pancreatic secretion was studied. The antimotilin serum completely blocked the pancreatic secretory cycles in two dogs so studied, whereas rabbit anti-CCK-PZ serum did not influence the pancreatic cycle in two dogs. We conclude that circulating motilin plays an important role on the development of cyclic increase in the pancreatic secretion in two dogs so studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of increased exocrine pancreatic secretion in pancreatic juice-diverted rats

We investigated a possible role of endogenous cholecystokinin-pancreozymin (CCK-PZ) in the mechanism of exocrine pancreatic secretion after excluding pancreatic juice from the intestine in rats. Fasting plasma immunoreactive CCK-PZ was determined in normal rats, in rats with pancreatic duct ligation, and in sham-operated rats. The mean fasting plasma CCK-PZ concentration of rats with pancreatic duct ligation, 25.1 +/- 2.0 pM, was significantly greater (p less than 0.001) than those of normal and sham-operated rats, 14.3 +/- 1.7 and 11.5 +/- 2.2 pM, respectively. Whereas mean postprandial plasma CCK-PZ concentrations of normal and sham-operated rats were significantly greater (p less than 0.001) than their fasting levels, no significant increase occurred in the rats with pancreatic duct ligation after a meal. The mean fasting plasma CCK-PZ concentration of rats with pancreatic duct ligation was comparable to the mean postprandial CCK-PZ level of normal and sham-operated rats. To determine a possible role of circulating endogenous CCK-PZ on the pancreatic secretion, anesthetized rats were prepared with ligation of pylorus and cannulation of pancreatic duct. After diversion of pancreatic juice began, pancreatic secretion including protein significantly increased, which coincided with a significant increase in plasma CCK-PZ concentration. The increases in both pancreatic secretion and plasma CCK-PZ were reversed by intraduodenal administration of bovine trypsin or rat pancreatic juice. Furthermore, the increase in pancreatic secretion was abolished by intravenous infusion of proglumide or an intravenous bolus injection of a rabbit anti-CCK-PZ serum, which also blocked clearly the increase in the pancreatic secretion stimulated by exogenous CCK-PZ8 (0.125 micrograms X kg-1 X h-1) in rats. Thus we conclude that the increase in pancreatic secretion resulting from elimination of pancreatic juice from the intestine is attributable, in part, to increased release of CCK-PZ, and thus it is suggested that trypsin in the intestinal lumen plays a significant role in release of CCK-PZ.

Endogenous cholecystokinin drives gallbladder emptying in dogs

We investigated the effect of fat in the duodenum on the gallbladder emptying in seven dogs prepared with gastric, duodenal, and gallbladder cannulas. Gallbladder volume was measured at 15-min intervals, and venous blood samples were obtained at regular intervals for 2.5 h. Intraduodenal administration of Lipomul (pH 5.0, corn oil) in three different doses (1.1, 2.2, and 4.4 mmol/10 min) resulted in significant increases in gallbladder emptying in a dose-dependent manner (r = 0.8668, P less than 0.001). Likewise, the increase in integrated cholecystokinin (CCK) release in response to Lipomul was also dose dependent (r = 0.7334, P less than 0.001). A statistically significant correlation was found between integrated CCK release and gallbladder emptying in response to Lipomul (P less than 0.001). To determine the role of circulating endogenous CCK on gallbladder emptying effects of intravenous administration of proglumide and a rabbit anti-CCK serum on gallbladder emptying were studied. Gallbladder emptying was virtually abolished by the antiserum. Proglumide not only abolished the emptying but also increased gallbladder volume. Thus we conclude that in dogs the gallbladder emptying in response to fat in the upper small intestine depends on increased circulating endogenous CCK.

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.

Release of secretin by licorice extract in dogs

To determine the effect of a fraction of licorice extract, FM100, on the endogenous release of secretin and exocrine pancreatic secretion, five dogs were prepared with chronic pancreatic fistulas and gastric cannulas. Intraduodenal administration of licorice extract (pH 7.4) in three different doses (0.5, 1.0, and 2.0 g) resulted in significant increases of both plasma secretin concentrations and pancreatic bicarbonate secretion in a dose-related manner. The plasma secretin concentration and pancreatic bicarbonate output produced by licorice extract correlated well. Intragastric administration of licorice extract (2 g) in 5% liver extract meal (in which pH was maintained at 5.5 by the intragastric titration method) resulted in significant increases of both plasma secretin concentration and pancreatic bicarbonate output. The increase in pancreatic bicarbonate secretion was completely abolished by intravenous infusion of a rabbit antisecretin serum in the two dogs so studied. Thus, the present study indicates that the endogenous release of secretion is involved in a mechanism of an increase in exocrine pancreatic secretin induced by FM100.

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.

Neurohormonal regulation of secretin secretion in canine duodenal mucosa in vitro

We examined the effects of cholinergic, peptidergic and GABAergic agents on secretin secretion from canine duodenal mucosal explants incubated in organ culture media. Carbachol (10(-12) to 10(-4) M), atropine (10(-6) to 10(-4) M), hexamethonium (10(-6) to 10(-4) M), and somatostatin did not alter basal secretion of secretin. Somatostatin (10(-7) to 10(-8) M) inhibited secretin secretion stimulated by pH 4.5. Met, Leu and their D-ala2-analogs inhibited both basal and pH 4.5-stimulated secretin. Naloxone reversed the inhibition caused by met-enkephalin at pH 7.4. GABA (10(-9) to 10(-6) M) stimulated both basal and pH 4.5-stimulated secretin secretion. GABA-stimulated secretin secretion was neuronal in nature, bicuculline sensitive and was mediated via post ganglionic cholinergic neurons. GABA-stimulated secretin secretion was inhibited by both somatostatin and metenkephalin, suggesting that GABA-stimulated secretin secretion may be under the inhibitory control of peptidergic agents as well.

Motility abnormality in dogs with gastrojejunostomy

Motility related to gastrojejunostomy were studied in seven dogs which were prepared with a gastric cannula and platinum electrodes placed in the antrum, duodenum, jejunum and ileum. Five dogs were equipped with gastrojejunostomy at the time of electrode implantation and the two remaining dogs were used as control. Myoelectric activity recorded revealed several abnormal findings and occasionally spike activity occurred simultaneously in the duodenum, jejunum and ileum or it retropropagated from lower ileum to reach the stomach. The study suggests that the dyspeptic symptoms observed in patients after gastrojejunostomy may be associated with similar motility abnormalities as observed in these dogs.

Effects of exogenous secretin on pancreatic and biliary ductal and sphincteric pressures in man demonstrated by endoscopic manometry and correlation with plasma secretin levels

An endoscopic manometric technique was used to investigate the effects of exogenous secretin on pancreatic duct, common bile duct, pancreatic duct sphincter, and bile duct sphincter pressures in 20 healthy volunteers. Synthetic secretin was infused intravenously at rates of 8.05, 16.1, 32.2, 64.4, 129, 258, and 516 ng/kg/hr, and plasma secretin concentrations were measured by a radioimmunoassay. Secretin produced a significant fall in peak and trough pancreatic duct sphincter pressures from basal values of 48.2 +/- 7.9 mm Hg (mean +/- SD) and 16.9 +/- 7.7 mm Hg, respectively, to 34.4 +/- 6.8 mm Hg and 11.2 +/- 5.8 mm Hg (P less 0.005), respectively, at a mean plasma secretin concentration of 16 pg/ml (during an infusion rate of 32.2 ng/kg/hr). Higher infusion rates had no additional effect. Pancreatic duct pressure became significantly elevated above basal (11.5 +/- 4.0 mm Hg) at the two highest secretin rates. Secretin had no effect on common bile duct or bile duct sphincter pressures. Plasma secretin concentrations were within the postprandial range during the lowest four secretin infusion rates. We conclude that secretin produces selective physiological relaxation of the pancreatic duct sphincter.