Transductal fluxes of anions in the rat pancreas

Transductal fluxes of water and monovalent ions in ferret salivary glands

The net transductal fluxes of water and monovalent ions were measured in the parotid and submandibular salivary glands of the ferret, Mustela putorius furo, during stimulation of secretion with pilocarpine. The duct systems of these glands were found to be impermeable to water using the split-oil droplet method for stationary microperfusion of lobular and main ducts. The net transductal fluxes of Na+, K+, Cl-, and HCO3- were characterized by analysis of ductal fluid samples obtained simultaneously from the intercalated, lobular, and main ducts of these glands.

Exogenous and endogenous stimulations during different phases of pancreatic secretion in conscious rats

The effects of stepwise increasing doses of intravenous caerulein, secretin, urecholine and intraduodenal oleic acid were investigated in conscious rats. a) Basal water, bicarbonate, and protein secretion significantly augmented after diversion of pancreatic juice. On the basis of protein secretory pattern of basal secretion 3 stable stages have been recognised: 1. The most physiological basal stage during return of pancreatic juice. 2. The first, highly elevated plateau from the 4th to 7th 30-min period after diversion of pancreatic juice. 3. The second, delayed and less elevated plateau after 270 min. b) The following patterns of stimulated secretion were observed: 1. Caerulein stimulated protein and bicarbonate secretion during return of juice and the first plateau but it failed to elicit a significant response during the second, delayed plateau. 2. Secretin and urecholine showed similar protein responses during return of pancreatic juice but after diversion, they stimulated water and bicarbonate secretion only. 3. During the second plateau oleic acid stimulation resulted in a significant increase in water and bicarbonate secretion but no significant increase occured in protein output. The delayed inhibition of protein secretion, previously described in our laboratory, was unchanged. 4. Supramaximal doses of exogenous stimuli caused an inhibition in pancreatic secretion.

Effect of chronic pentagastrin, cholecystokinin, and secretin on pancreas of rats

Pentagastrin (1.5 mg/kg), 20% pure natural cholecystokinin (CCK, 37.5 Ivy dog U/kg) or secretin (25 microgram/kg) was given in a depot carrier subcutaneously to rats 3 times daily for 15 days. The dose of CCK and secretin was submaximal for pancreatic secretion, whereas the dose of pentagastrin was supramaximal for gastric acid secretion. The pancreatic wet weight increased by 12% (P less than 0.01) in the rats treated with pentagastrin, 57% (P less than 0.001) in those treated with CCK, and 9% (P less than 0.01) in those treated with secretin. In CCK-treated rats, the maximal protein and bicarbonate outputs in response to cholecystokinin increased proportionately to the increase in pancreatic weight, but maximal bicarbonate and protein outputs in response to secretin were unaltered. The secretin-treated rats showed a lowered basal secretion of bicarbonate and a lowered sensitivity to secretin stimulation, but the maximal bicarbonate and protein outputs to secretin and CCK were unchanged. Treatment with pentagastrin produced no significant changes in pancreatic responses to secretin or CCK. We conclude that 1) the increase in pancreatic weight produced by repeated injections of cholecystokinin was accompanied by proportional increase in functional capacity as reflected by the increased maximal bicarbonate and protein outputs in response to cholecystokinin, and 2) repeated administration of secretin decreased the sensitivity of the pancreas to secretin without altering maximal bicarbonate response.

Secretion of electrolytes by the pancreas of the anaestetized rat

1. HCO-3, Na+ and K+ concentrations were measured in bile-free pancreatic juice collected from fasted and fed anaesthetized rats. 2. Resting flow rates averaged 0.62 mul. g-1 .min-1 (fasted) and 2.8 mul. g-1. min-1 (fed) and the mean HCO-3 concentrations, respectively, were 25.8 and 33.3 mM. 3. In fasted rats, instillation of HCl into the duodenum caused flow rate to increase threefold and HCO-3 concentrations to double (66 mM). Intravenous infusion of pure natural (GIH) secretin caused a fivefold increase in flow rate; HCO-3 concentrations, again, doubled (67.5 mM). Infusion of synthetic secretin produced effects essentially the same as those produced by GIH secretin. 4. Infusion of Boots secretin caused a thirteenfold increase in flow rate (8.32 mul.g-1. min-1) but HCO-3 concentrations rose only slightly (43.3 mM). However, following cessation of infusion, when flow rate approximated the maximum obtained with pure secretin, the HCO-3 concentration was much higher (57.2 mM at 3.19 uml.g-1.min-1). In fed animals the responses were similar but maximum flow rates were greater (12 mul. g-1. min-1). 5. Infusion of caerulein produced a secretory rate slightly less than with Boots secretin (5.06 mul. g-1.min-1) and HCO-3 concentrations were plasmalike (30.2 mM); infusion of the synthetic octapeptide of cholecystokinin (OP-CCK) gave similar flow rates and HCO-3 concentrations. 6. Infusion of a mixture of caerulein and GIH secretin mimicked closely the effect of Boots secretin. At maximum flow rates (7.6 mul. g-1. min-1) the HCO-3 concentration was 43.7 mM and at lower flow rates (3.90 mul.g-1. min-1) it rose to 54.2mM. 7. It is concluded that the response of the rat pancreas to secretin is qualitatively similar to that of all other vertebrates so far studied, but, relative to other animals, the response is sluggish. In contrast, the rat pancreas responds well to cholecystokinin (CCK) stimulation, yielding a juice with plasma-like HCO-3 concentration. Boots secretin, which is heavily contaminated with CCK, causes a mixed response resembling that of CCK at high secretory rates and that of pure secretin at lower rates. 8. An unexplained feature of rat pancreatic juice was that K+ concentrations, although plasma-like in unstimulated samples, rose to about 8mM when flow rate increases as a result of secretin, but not CCK, stimulation. In all other animals so far studied, the K+ concentration has been found to be independent of flow rate.