Pure Natural Porcine Secretin Research Articles

Comparative effects of synthetic and natural secretin on pancreatic secretion and on secretin, insulin, and glucagon levels in man

The effect of synthetic secretin (Roche) on exocrine pancreatic secretion and on secretin, insulin, and glucagon levels was determined and compared with that of pure natural porcine secretin (GIH, Karolinska Institutet, Stockholm) in 10 healthy volunteers. The two secretin preparations were found to be equipotent. Equipotency applies to pancreatic secretion and to secretin and insulin plasma levels, whereas the plasma levels of glucagon were not affected by either drug. It is concluded that this synthetic secretin preparation is suitable for clinical and research purposes.

Effects of porcine secretin on exocrine and endocrine function in the isolated perfused rat pancreas.

The effects of both synthetic and pure natural porcine secretin on immunoreactive insulin (IRI) and immunoreactive glucagon (IRG) release and on pancreatic exocrine secretion were studied in the isolated perfused rat pancreas. Synthetic porcine secretin stimulated a significant increase in pancreatic juice flow and amylase output at concentrations as low as 0.01 and 0.1 ng/ml, respectively. The maximal peak rate of both juice flow and amylase output was observed at 1 microgram/ml synthetic secretin. Synthetic secretin at concentrations up to 2 micrograms/ml and pure natural porcine secretin at a concentration of 1 clinical unit/ml had no effect on IRI secretion regardless of the glucose concentration (50, 100, or 150 mg/100 ml) in the perfusate. Both types of secretin, however, elicited a concentration-dependent increase in IRG secretion in the presence of 50 mg/100 ml glucose. The lowest synthetic secretin concentration causing a significant increase in IRG release was 0.1 ng/ml, and maximal stimulation was observed at 1 microgram/ml. These concentrations were similar to those eliciting minimal and maximal amylase release. Thus, synthetic and pure natural porcine secretin have been shown to not only stimulate pancreatic juice flow and amylase secretion but also to elicit IRG release from the isolated perfused rat pancreas.

Hormone-stimulated release of pancreatic polypeptide before and after vagotomy in dogs.

Concentrations of pancreatic polypeptide (PP) in peripheral blood were measured before, during, and after infusions of graded doses of synthetic human gastrin I (SHG-I), cholecystokinin 99% pure (CCK-99%), CCK octapeptide (CCK-OP), and pure natural porcine secretin in six dogs with gastric and duodenal fistulas. Studies were repeated after truncal vagotomy. Significant increases in concentrations of PP were found with 1 microgram . kg-1 . h-1 of SHG-I, 0.25 and 1.0 microgram . kg-1 . h-1 of CCK-99%, and 0.06 and 0.25 micrograms . kg-1 . h-1 of CCK-OP. Significant increases persisted after vagotomy, except at the lower dose of CCK-OP. Postvagotomy responses were significantly less than prevagotomy, except at the higher doses of CCK-99% and CCK-OP. Pure secretin did not change concentrations of PP in blood before or after vagotomy. The most potent stimulant for PP release on a molar basis was CCI-99%, followed by CCK-OP and SHG-I. The results suggest that cholinergic and humoral agents of the gastrin-cholecystokinin family interact in the normal physiological response of PP to food and that, in dogs, CCK-like peptides are more potent than gastrin.

Secretin and cholecystokinin activities in extracts of sheep intestine

Extracts of sheep intestine prepared to contain secretin were readily obtained, reacted with antibodies raised to pure natural porcine secretin, were potent stimulants of pancreatic exocrine secretion of the anaesthetised rat and failed to contract sheep gall bladder in vitro. In contrast extracts prepared to contain cholecystokinin (CCK) caused contraction of sheep gall bladder in vitro but were more difficult to obtain than those of secretin due to a contaminant green pigment. The experiments provide biological and immunological evidence for the existence of secretin in sheep intestine. The demonstration of CCK activity on sheep gall bladder by separate extracts is indicative of the presence of CCK in the sheep but this awaits confirmation by immunological means.

Effect of secretion on the exocrine and endocrine pancreas Part V: Pancreatic exocrine and endocrine responses to secretion in rats in vivo and in vitro (author's transl)

Secretin is an established stimulator of exocrine pancreatic function and has been reported by some to also stimulate insulin release both in vivo and in vitro. Contrary to these observations with natural porcine secretin, synthetic porcine secretin has been revealed to have no influence on insulin release but does stimulate glucagon release from the isolated perfused rat pancreas. Unphysiologically large doses of synthetic porcine secretin has also been confirmed in in vivo experiments to be capable of stimulating not only glucagon but also insulin secretion from the rat pancreas. Thus, the discrepancies between our previous results with synthetic porcine secretin and those obtained with natural porcine secretin may be due to the differences of the preparations of secretin or to the species differences of the experimental animals, or of the experimental system itself.The present investigation was undertaken to determine the effect of natural porcine secretin on exocrine and endocrine secretions from the rat pancreas in vivo and in vitro.Pancreases from Wistar male rats were isolated and perfused according to the technique of Kanno. A Krebs Ringer bicarbonate solution containing 4.6% dextran T-70, 0.25% bovine serum albumin and 50 mg/100 ml glucose was used as a perfusion medium. Commercially available secretin (Secrepan®; Eisai Co., Ltd., Tokyo, Japan : supplied as lyophilized powder containing 30% pure natural porcine secretin and stabilizer), an inactive placebo of secretin containing cystaine and alanine as stabilizers for natural secretin, and 100% pure natural porcine secretin without stabilizer were used as stimulants of pancreatic exocrine and endocrine secretions.Overnight-fasted Wistar strain rats were used in the in vivo experiments. The rats were anesthetized with sodium pentobarbital by subcutaneous injection. The body temperature was held at 37°C by a heating pad. One of the following solutions was administered into the jugular vein by a single rapid injection : 1 and 50 U/kg natural porcine secretin (Se-crepan®), and a comparable dose of the placebo of secretin. Blood samples were collected from the portal vein at -10, 0, 2.5, 5, 10, 30 and 60 min.Immunoreactive insulin (IRI) was measured by polyethylene glycol radioimmunoassay. Immunoreactive glucagon (IRG) was determined by radioimmunoassay by means of dextran coated charcoal using antiserum 30 K. Rat insulin and porcine glucagon were used as standards in the IRI and IRG assays, respectively.The lowest secretin concentration causing a significant increase in pancreatic flow rate and amylase output from the isolated perfused rat pancreas was 1 mU/ml. The maximal pancreatic flow rate and amylase output required a secretin concentration of 1 U/ml. Higher concentrations of secretin, however, resulted in lower responses of both pancreatic juice flow and amylase output. Commercial secretin at concentrations of 1 mU/ml to 2 U/ml in the presence of 50 mg/100 ml glucose did not cause an increase in the IRI concentration in the portal effluent above the basal value. Secretin at the concentration of inducing the maximal pancreatic exocrine secretion with 50 mg/100 ml glucose (1 U/ml) was infused for 10 min in the presence of 100 and 150 mg/100 ml glucose to determine whether a threshold level of glucose was required for the insulinotropic action of secretin. Commercial secretin at a concentration of 1 U/ml elicited a significant short-termed increase in the IRI response to 100 and 150 mg/100 ml glucose, while 1 U/ml pure natural porcine secretin with-out stabilizer had no effect on IRI secretion, even when perfused with 100 or 150 mg/100 ml glucose.

Physiological Significance of Secretin in the Pancreatic Bicarbonate Secretion

The pancreatic response to physiological concentrations of secretin obtained after minute boluses of exogenous secretin was studied in 16 normal volunteers. Output of bicarbonate into the duodenum was measured by duodenal aspiration in 5 subjects and by endoscopic cannulation of the pancreatic duct in 11 subjects. Pure natural porcine secretin was injected intravenously in doses of 125, 250, and 500 fmol x kg-1 body weight (0.0013, 0.0027, and 0.0054 clinical units x kg-1). All three doses of secretin increased plasma secretin concentration, duodenal bicarbonate concentration, and duodenal bicarbonate output significantly. The bicarbonate output measured by the two techniques did not differ significantly. The increments in median plasma secretin concentration were 1.6, 3.0, and 6.4 pmol x 1(-1) after secretin, 125, 250 and 500 fmol x kg-1, and the corresponding 15-min bicarbonate output 283, 442, and 1435 micromol, respectively. The concentrations of secretin in plasma found after these doses of secretin are of the same order of magnitude as the secretin concentrations found during physiological conditions in man. It is concluded that the physiological concentrations or secretin influence pancreatic bicarbonate secretion.

Secretory effects of secretin on isolated perfused porcine pancreas.

The effect of pure natural porcine secretin on endocrine and exocrine pancreatic secretion was studied in the totally isolated perfused porcine pancreas. The exocrine pancreatic responses to secretin correspond well with those obtained in the anesthetized pig. The lowest concentration of secretin observed to increase pancreatic secretion was 2.8 pmol/liter, whereas the maximum pancreatic responses were obtained at a secretin concentration of 92 pmol/liter. The infusion of secretin in concentrations ranging from 2.8 to 278 pmol/liter in the presence of a constant concentration of glucose (7.5, 5.0, or 3.5 mmol/liter) was without effect on the insulin and glucagon release. Infusion of secretin at a concentration of 834 pmol/liter in the presence of glucose at 7.5 mmol/liter provoked a significant (P less than 0.01) short-lived increase in insulin secretion. However, there was no effect on the glucagon secretion. The results of this study indicate that neither the augmented insulin response nor the suppression of glucagon elicited by oral glucose depend on secretin.

Elimination of porcine secretin in pigs.

1. The elimination of immunoreactive secretin was studied in anaesthetized pigs by using constant infusions of pure natural porcine secretin. 2. The mean metabolic clearance rate was 15.4 ml min-1 kg-1, and was independent of the level at which it was determined. The mean distribution space was 64.4 ml/kg. The half-life of secretin after termination of the infusion averaged 2.6 min. 3. During intravenous infusion of secretin in a dose of 27.8 pmol h-1 kg-1 the renal extraction was 52%. Exclusion of the kidneys increased plasma secretin concentration from 26.5 pmol/l to 47.3 pmol/l and increased the half-life to 4.4 min. 4. Exclusion of the liver during infusion of secretin in a dose of 27.8 pmol h-1 kg-1 resulted in an increment in plasma secretin concentration of 7.8 pmol/l and an increase of the half-life to 3.6 min. 5. A gradient of endogenous secretin across the liver was present but no arteriovenous difference was found across the foreleg. 6. Incubation of secretin with whole blood or serum for 20 min at 37 degrees C did not result in any degradation of secretin.

Radioimmunossay of secretin in human plasma.

A radioimmunoassay is presented which employs 125I-labelled synthetic secretin, antibody against synthetic secretin, and standards prepared from pure natural porcine secretin. Secretin to be measured was extracted into methanol from heparinized plasma containing aprotinin, which together with cysteine hydrochloride was used as stabilizer throughout the assay. With polyethylene glycol separation, a within assay precision of 10% at 17 pmol/1 was found. The between assay precision was 15% at 17 pmol/1 and thelimit of detection 2.5 pmol/1 plasma. Accuracy was 70-85%. The immunoreactive secretin levels in human plasma increased from 4.5+/-0.5 pmol/1 (mean+/-S.E.M.) to 19.5+/-7.5 pmol/1 (mean+/-S.E.M.) after duodenal acidification (n=5). Pancreatic flow rate increased from 0.5+/-0.1 ml/min (mean+/-S.E.M.) to 4.8+/-0.5 ml/min (mean+/-S.E.M.), and bicarbonate output from 9.6+/-1.8 mumol/min (mean+/-S.E.M.) to 268+/-51 mumol/min (mean+/-S.E.M.) after duodenal acidification.

Inhibition of secretin release and pancreatic bicarbonate secretion by somatostatin infusion in man.

Five healthy students were investigated on two different days with or without a constant infusion of somatostatin (500 microgram/h) into an arm vein a fluoroscopically placed Lagerlöf tube was used for the collection of gastric and duodenal juice. After 30-min basal period, 40 ml 100 mmol/l HCl was infused into the midpart of the duodenum over 5 min through a thin catheter attached to the tube. Plasma immunoreactive secretin was measured by radioimmunoassay employing 125I-labelled synthetic secretin, antibody against synthetic secretin, and standards prepared from pure natural porcine secretin. Secretin levels without somatostatin infusion were 4.6+/-0.7 pmol/l (mean+/-S.E.M.) basally and rose to a peak of 21.8+/-6.2 pmol/l after duodenal acidification (p less than 0.05) and with somatostatin infusion were 4.4+/-0.4 pmol/l basally and rose to a peak of 6.7+/-1.7 pmol/l (n.s.) after duodenal acidification. Pancreatic bicarbonate output increased from 8.0+/-2.5 mumol/min (mean+/-S.E.M.) to 283+/-44 mumol/min without somatostatin infusion (p less than 0.05) and from 6.7+/-2.1 mumol/min to 70+/-13 mumol/min somatostatin (p less than 0.05). This study shows that somatostatin (500 microgram/h can inhibit the release of secretin and the pancreatic bicarbonate secretion after duodenal acidification in man.

Radioimmunoassay of secretin in plasma.

A sensitive and specific radioimmunoassay for secretin has been developed. 125I synthetic porcine secretin was used as label. Antibodies were raised against synthetic pocrine secretin. Pure natural porcine secretin was used as standard and free and bound hormone was separated by plasma-coated charcoal. Nonspecific interference with the assay system by plasma factors was abolished by extraction of plasma samples. The detection limit was 1.3 pmol/l. Within and between assay reproducibility (five triplicate determinations in each of eight assays) was 0.7 and 0.9 pmol/l respectivel (1 SD) at a concentration of 4.7 pmol/1. Fasting level in seventy normal persons ranged from less than 1.3 to 5.3 pmol/1. High concentrations were found in two patients with Zollinger-Ellison syndrome. In six normal persons intraduodenal acidification was immediately followed by an increase in secretin concentrations in peripheral venous blood to 7.7-23.6 pmol/1 (range), with a median of 15.5 pmol/1. In six anaesthetized pigs a fifty-fold increase in portal plasma secretin concentration after duodenal acidification was followed by a thirty-fold increased in the flow rate of pancreatic juice.

Plasma Insulin Concentration During Physiological Variations in Immunoreactive Plasma Secretin

The effect of endogenous and exogenous secretin on fasting plasma insulin and glucose concentrations in peripheral venous blood was studied. In 10 non-diabetic subjects intragastric instillation of 300 ml 0.1 mol/l hydrochloric acid increased the plasma secretin concentration significantly. This increment did not influence insulin or glucose concentration. Control experiments with intragastric instillation of 300 ml of isotonic saline did not influence the plasma concentration of secretin, insulin or glucose. In four other non-diabetic persons no significant changes were found in plasma insulin or glucose concentration during an i.v. infusion of pure natural porcine secretin in doses of 0.1, 0.3, 1.0 and 3.0 clinical units/kg/h. The results suggest that secretin is without effect on insulin secretion in the fasting normal subject.

Comparison of the actions of porcine secretin and extracts of chicken duodenum on pancreatic exocrine secretion in the cat and turkey.

1. Extracts were prepared of chicken duodenum and their actions on pancreatic secretion in urethane anasthetized turkeys and in conscious cats were compared with those of pure natural porcine secretin. 2. The chicken extracts and porcine secretin stimulated dose-dependent increases in the rate of flow, but not the rate of protein secretion, from the pancreas in cats and turkeys. 3. Porcine cholecystokinin stimulated both the rate of flow and the rate of protein secretion from the pancrease in turkeys. 4. The doses of chicken extract required to evoke half maximal rates of flow of pancreatic juice were similar in the turkey (0-55 mg/kg) and in the cat (0-72 mg/kg). The highest concentration of bicarbonate recorded in the turkey responses was 30 m-equiv/l. compared with 112 m-equiv/l. in the cat. 5. The dose of porcine secretin required for half maximal rate of flow in the bird (5-9 mug/kg) was 180 times higher than in the mammal (0-33 mug/kg). In the cat the duration of responses to porcine secretin was significantly greater than to the chicken extract. 6. It is concluded that in birds there is a factor with biological properties similar but not identical to those of porcine secretin, and that this factor may regulate pancreatic secretion by a mechanism resembling the secretin mechanism in mammals.

Pancreatic Dose-Response Curves to Intravenous Secretin in Man

Pure natural porcine secretin infused at a constant rate intravenously in successively increasing doses produced a pancreatic dose-response curve for rate of flow and rate of bicarbonate output almost identical with that obtained by rapidly injected intravenous doses in 6 healthy subjects. The mean maximal bicarbonate output was achieved at the dose of 0.9 U of secretin per kg either as a rapid intravenous injection or by constant infusion during 1 hr further. Increment in dose increased the pancreatic response insignificantly. It is suggested that a stepwise increase in the dose of intravenously infused secretin is an effective and convenient procedure to obtain the entire pancreatic dose-response curve to secretin in a 1- to 3-day examination in man.