The origin and secretion of pancreatic juice bicarbonate

SUMMARY1. The effect of replacing extracellular bicarbonate and chloride by other anions on the volume and composition of secretin-stimulated pancreatic juice has been analysed in the isolated, perfused cat pancreas.2. The anions of some aliphatic carboxylic acids were able partially to substitute for bicarbonate in sustaining pancreatic secretion. The order of effectiveness was: acetate > propionate > butyrate > formate.3. The rate of secretion in the presence of 25 mM-acetate was 42 % of that achieved with 25 mM-bicarbonate. The concentration of acetate in the secretion varied with flow rate, reaching a maximum of 120 mm at high flow rates and declining at lower flow rates, with reciprocal changes in chloride concentration. Bicarbonate was always present in the secretion at a concentration of 5-7 mM. 4. Inorganic anions were able totally or partially to substitute for chloride in sustaining secretion. In relation to chloride, their degree of effectiveness was: chloride -bromide = or > nitrate > iodide > sulphate > methyl sulphate > isethionate. Those anions which had no effect on secretion rate (i.e. bromide and nitrate) also had no effect on the bicarbonate concentration of the secretion and themselves appeared in the secretion in place of chloride. Those anions which inhibited secretion increased the bicarbonate concentration in the secretion in proportion to the degree of inhibition they caused (i.e. the increase was greatest with isethionate).5. When perfusate chloride was only partially replaced by bromide or iodide the ratios of chloride: bromide and chloride: iodide in the secretion were approximately equal to those in the perfusate.6. The carbonic anhydrase inhibitor acetazolamide reduced secretary rate and bicarbonate concentration when added to normal perfusion fluid or chloridesubstituted fluids, but had no effect following replacement of perfusate bicarbonate by acetate.7. These observations illustrate that an extracellular source of permeant anions is

Section: Discussionmentioning

confidence: 99%

“…The carbonic anhydrase inhibitor acetazolamide causes inhibition of secretion in the isolated cat pancreas accompanied by a reduction in bicarbonate concentration 572 R. M. CASE AND OTHERS and a reciprocal rise in chloride concentration (Case, Scratcherd & Wynne, 1970; and see Fig. 11).…”

Section: The Influence Of Acetazolamidementioning

confidence: 99%

Electrolyte secretion by the isolated cat pancreas during replacement of extracellular bicarbonate by organic anions and chloride by inorganic anions.

Case¹,

Hotz²,

Hutson³

et al. 1979

“…The proton is common to all and it is postulated that this is the actively transported ion (Scratcherd, Hutson & Case, 1981). Simultaneously with the secretion of bicarbonate into the ductular lumen, the pH of the fluid leaving in the venous drainage of the gland falls accompanied by an increase in the partial pressure of the carbon dioxide (Case, Scratcherd & Wynne, 1970). This has been interpreted as the secretion of protons backwards across the basolateral membrane.…”

Section: Introductionmentioning

confidence: 99%

“…It is derived almost entirely from the extracellular fluid with only about 40 arising directly from metabolism of the ductular cells (Case, Scratcherd & Wynne, 1970). Anions other than bicarbonate will support some secretion of pancreatic juice.…”

Section: Introductionmentioning

confidence: 99%

Absence of a relationship between arterial pH and pancreatic bicarbonate secretion in the isolated perfused cat pancreas.

Ammar

Hutson

Scratcherd

1987

relationship between inflow pH and bicarbonate secretion at constant Pco2 down to a pH of 7-3 until the bicarbonate concentration of the perfusate was reduced below 10 mM, when the secretion rate fell off rapidly. 5. A linear relationship was found to exist between the volume rate of secretion and the Pco2 of the pancreatic juice and the output of lactate both in the isolated saline-perfused gland and the blood-perfused pancreas in situ.6. At high rates of secretion the PCO2 of the pancreatic juice was always higher than that of either the arterial inflow or the venous outflow. There is therefore no gradient for the passive movement of carbon dioxide between the arterial inflow and the pancreatic juice.7. Inhibition of secretion with acetazolamide caused a fall in the PCO2 of pancreatic juice and increased the output of lactate. The secretion of lactate was not due to hypoxia as it also occurred in the blood-perfused gland in situ which had normal haemoglobin concentrations and oxygen saturation. 8. It is concluded that the secretion of bicarbonate is independent of arterial pH but critically dependent upon the arterial concentration of the bicarbonate ion. These experiments do not support the concept that the secretion of protons over the basolateral membrane is the major primary event in pancreatic secretion of bicarbonate.

“…Pancreatic secretion is sensitive to both the pH and bicarbonate concentration of the plasma, so that by lowering either or both parameters pancreatic secretion is inhibited (Rawls, Wistrand & Maren, 1963;Pak, Hong, Pak & Hong, 1966;Case, Scratcherd & Wynne, 1970;Case, Hotz, Hutson, Wynne & Scratcherd, 1979).…”

Section: Changes In Acid/base Statusmentioning

confidence: 99%

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

Grundy¹,

Hutson²,

Scratcherd³

1983

SUMMARY1. Cooling the cervical vagi of the anaesthetized splanchnectomized cat to 2 TC caused a 54-4 + 8-8 % inhibition of pancreatic electrolyte secretion stimulated submaximally with pure secretin.2. 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.3. 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.4. 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.5. Electrolyte secretion was also inhibited by bilateral vagal section. 6. 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.7. 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.