Stimulation of endocrine, but not exocrine, pancreatic secretion during 2-deoxy-D-glucose-induced neuroglycopenia in the conscious pig.

The effects of autonomic nervous activation, initiated by 2-deoxy-D-glucose (2-DG)-induced neuroglycopenia, or endocrine and exocrine pancreatic secretion were investigated in the conscious pig. Pigs were surgically fitted with permanent pancreatic duct and duodenal reentrant cannulas, allowing long-term sampling of pancreatic juice, and a jugular vein catheter for blood sampling and infusion of 2-DG. 2-DG was administered as a 5-min intravenous infusion at three dose levels to conscious pigs. 2-DG (400 mg/kg) was found to elevate plasma glucagon and insulin levels (p < 0.01). In contrast, exocrine pancreatic secretion, measured as volume, total protein output, and output of trypsin activity was not affected by 2-DG at the dose levels of 75, 200, and 400 mg/kg. Secretin (440 pmol/kg/h), however, stimulated pancreatic exocrine output of fluid (p < 0.01), protein (p < 0.01), and trypsin (p < 0.05). It is concluded that autonomic nervous activation by 2-DG-induced neuroglycopenia, in the conscious pig under basal conditions, elevates the plasma levels of glucagon and insulin but does not affect exocrine pancreatic secretion. 2-DG-induced neuroglycopenia is, thus, a suitable model for studying autonomic neural influences on the porcine endocrine pancreas.

Pancreatic exocrine secretion during the first days after weaning in pigs.

Feed replacement at weaning plays an important role in the induction of pancreatic maturation. To understand the changes in the exocrine pancreas at weaning and the relation to postweaning problems, we studied the function of the exocrine pancreas and changes of intestinal hemolytic Escherichia coli in four pigs. The pigs were chronically fitted with pancreatic duct catheters and T-shaped cannula inserted into the duodenum for reintroduction of pancreatic juice. One day before weaning (at 30 d of age), pancreatic juice was collected for 1 h before and 1 h after a morning and an evening suckling. The pigs were not creep fed, but from weaning the pigs received a standard weaning diet ad libitum. On d 1, 2, 3, and 5 after weaning, pancreatic juice was collected continuously for the 24-h period. The total pancreatic secretion was measured at hourly intervals, 1.5-mL samples were taken for analysis, and the remaining juice was returned to the animal. On these days, samples from the duodenum, ileum, and rectum were also taken for analyses of hemolytic E. coli. From the day before to 5 d after weaning, a gradual increase in pancreatic secretion was observed concerning volume (P < .001) and protein (P < .01) and trypsin (P < .02) levels. An increase (P < .01) in hemolytic E. coli in the duodenal contents was also documented during this period. We assume that the gradual increase in the measured variables of pancreatic secretion is related to the increasing consumption of solid feed. However, the appearance of E. coli and disappearance of milk components from the gastrointestinal tract could be other factors stimulating the exocrine pancreas.

Circadian and ultradian variation in pancreatic secretion of meal-fed pigs after weaning.

We studied the time structure of pancreatic secretion in two experiments involving seven 6- to 7-wk-old intact male pigs, surgically fitted with a jugular vein catheter for blood sampling, pancreatic catheter, and a duodenal T-cannula for chronic pancreatic juice sampling for 72 h at 30- to 60-min intervals. Pigs were kept in metabolic cages in a regimen of 12 h of light alternating with 12 h of darkness and were fed at 0800, 1500, and 2200 daily a standard diet based on barley, soybean meal, and fish meal. Beginning 4 d after surgical recovery, three 24-h collections of pancreatic juice and blood sampling were begun either at 0700 or 0800 every 2nd d for 5 d. Pancreatic secretion exhibited a pattern characterized by distinct meal-related secretions of the first phase (postprandial), containing large amounts of protein and enzymes (trypsin and chymotrypsin), and by non-food-stimulated secretions of the second phase with less protein and enzymes. During the dark span, the first phase was practically absent; the response of the pancreatic secretion to the 2200 meal was not very pronounced. Apart from the anticipated circadian rhythm demonstrable by single cosinor analysis on a group basis, a prominent 8-h component was almost invariably statistically significant. Moreover, an approximately 3.43-h component was also prominent. These data indicate that pancreatic secretions are circadian periodic and that their response to a standard meal is also circadian-stage dependent. The circadian components may have been free-running because the pigs were adjusting themselves to the changing phase and that resulted in the period being different from exactly 24 h.

The pattern of the circadian rhythm of pancreatic secretion in fed pigs.

The pattern of the circadian rhythm of pancreatic secretion was studied in four 6- to 7-wk-old intact male pigs that were kept in metabolic cages under 12 h light:12 h dark cycles and fed three times a day at 0800, 1500, and 2200. Three 24-h collections of pancreatic juice and blood were begun at 0800 every 2nd day during 5 d. A biphasic pattern of the exocrine pancreas was detected. Secretions during the first phase (postprandial peak) contained large amounts of protein and enzymes, and secretions appeared immediately after feed ingestion. Secretions during the second phase (between meals) had lesser amounts (P < .001) of protein and enzymes, but were of longer duration (P < .001). The output of protein and trypsin activity were generally correlated (P < .001) with each other, but the correlation of either with the volume outflow were small. However, these variables were correlated (P < .01) with the volume outflow at night during the second phase. Plasma concentrations of insulin and glucose increased after each meal, but the increase was significant (P < .05) only for insulin. Insulin and glucose concentrations were correlated (P < .01) with each other after the meals at 0800 and 1500. The results indicated a biphasic pattern of the exocrine pancreas and a monophasic pattern of the endocrine pancreas in pigs. The regulation of these patterns seems to vary during the 24-h period. Furthermore, feed enhanced secretion, but it did not seem to be the only factor controlling the circadian pattern.

Pineal influence on the diurnal rhythm of nonspecific immunity indices in chickens.

The effect of pinealectomy and melatonin injections on the diurnal rhythms of serum lysozyme and blood granulocytes was examined in White Leghorn cockerels kept from time of hatching for 5 weeks in L:D 12:12 conditions and immunized twice with sheep red blood cells (SRBC). Pinealectomy or sham-operation was made during first week of life. Pinealectomized chickens were injected daily with a melatonin dosage increased over 4 consecutive weeks (the dosage was 10, 13, 16, and 20 ng per bird daily during the 4 weeks, respectively; MEL I) at the beginning of darkness. The same treatment was performed on chickens with an intact pineal gland using additional melatonin doses increased 10 times (MEL II) and 500 times (MEL III). Intact chickens were also injected with MEL II and MEL III 4 hr before the end of light. Control birds received equivalent injections of vehicle. Five-week-old chickens were sacrificed during a 24-hr period every 4 hr. The existence of diurnal rhythm was evaluated by cosinor analysis. Pinealectomy shifted the acrophase of the diurnal rhythm of granulocytes and abolished that of serum lysozyme. Both rhythms were restored in pinealectomized chickens by MEL I but not by vehicle injections. The same melatonin dose was unable to change the granulocyte rhythm but delayed the acrophase of that of serum lysozyme in chickens with an intact pineal gland. Two higher melatonin doses influenced the diurnal rhythm of granulocytes as a function of dose and time of administration. The rhythm of serum lysozyme was dependent only on the time of injection. The pineal gland seems to control, via its hormone melatonin, the diurnal rhythm of nonspecific immunity in chickens.

Effect of dose and time of melatonin injections on the diurnal rhythm of immunity in chicken.

The effect of daily melatonin injections on the diurnal rhythm of immune parameters was examined in White Leghorn cockerels, kept from hatching in L:D 12:12 conditions. Subcutaneous injections of melatonin were made at the beginning of darkness or 4 h earlier for four weeks starting from one week of life. The melatonin dosage in one group was raised (10, 13, 16, and 20 ng per bird daily, respectively) during four consecutive weeks. The two other doses were 10 and 500 times higher and were increased every week as well. Control birds received equivalent injections of vehicle. Three-week-old chickens were immunized ip with sheep red blood cells and reimmunized one week later. Five-week-old birds were sacrificed during a 24 h period every 4 h. The existence of the diurnal rhythm was evaluated by cosinor analysis. The diurnal rhythm of total white blood cells and serum agglutinins was more dependent on the time of melatonin injections than on the hormone used. The effect of melatonin injections on the level of immune parameters examined was also dependent on the time of sample collection. Results obtained indicate the participation of pineal gland in the regulation of the diurnal rhythm of the examined indices of avian immune system function that exhibit diurnal changes in sensitivity to exogenous melatonin.

Exogenous melatonin modifies the circadian rhythm but does not increase the level of some immune parameters in the chicken.

The effect of daily injection of the pineal hormone melatonin and naltrexone, an opioid antagonist, on the circadian rhythm and the level of immune parameters (plaque forming cell [PFC] number, serum agglutinin titer, lymphoid gland weight, total white blood cells (WBC) and their fraction number, and serum lysozyme [LZ] content) was examined in White Leghorn cockerels and female BALB/c mice kept in LD 12:12. Animals were immunized ip with sheep red blood cells (SRBC) to stimulate their immune system. Subcutaneous injections of melatonin, naltrexone, or both drugs together were made 2 hr before the end of light, for 4 or 5 days, beginning on the day of immunization. The day following the fifth injection, chickens were sacrificed over a 24 hr period every 4 hr (experiment I) or twice daily, i.e., at the beginning of light and dark phases (experiment II). Mice were killed on the day following the fourth injection at the beginning of light, and splenic PFC number was determined (experiment III). In experiment I, the existence of the diurnal rhythm was evaluated by cosinor analysis. Melatonin injections entrained the circadian rhythm in anti-SRBC serum agglutinins, but it did not influence circadian rhythmicity in other parameters examined. The circadian rhythm in total WBC number and their fractions was entrained by naltrexone treatment. Melatonin injections did not affect either the diurnal mean of parameters examined or the weight of lymphoid organs. Splenic PFC number in chickens was diminished by both melatonin and naltrexone injections, whereas in mice it was increased by melatonin, and naltrexone antagonized that effect.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of potato fibre on exocrine pancreatic secretions and on plasma levels of insulin, secretin and cholecystokinin in growing pigs.

The effect of a potato fibre preparation on exocrine pancreatic secretions and on gastrointestinal hormone levels in plasma was studied in three 8 weeks old piglets that were surgically fitted with a jugular vein catheter for blood sampling, a pancreatic duct catheter and a T-shaped duodenal cannula for collection of pancreatic juice. The animals were fed for 2 weeks a control diet (experimental period 1), thereafter for 2 weeks the control diet supplemented with 2% potato fibre (experimental period 2) and for another 2 weeks the control diet again (experimental period 3). Additionally, intraduodenal (i.d.) infusions of the experimental diet, the control diet and potato fibre as well as i.v. infusions of a solution containing cholecystokinin (CCK) and secretin were administered. Potato fibre in the diet evoked in tendency an increase in the volume of secretion of pancreatic juice and a significant increase both in the mean values of the total protein content and total activities of lipase, trypsin and alpha-amylase when compared to the control diet. The i.d. infusion of the control diet, experimental diet and fibre infusate as well as the i.v. administration of the hormone infusate led to a spontaneous secretory response of the exocrine pancreas. Besides gastrointestinal hormones, such as CCK, other factors such as short chain fatty acids may be involved in the regulation of the exocrine pancreas.