Water and electrolyte secretion by the perfused pancreas of the cat

Abstract

SUMMARY1. A technique is described for perfusing the isolated cat pancreas with saline solutions.2. Single doses of secretin, although present in the perfusate for only a short time, caused a prolonged flow of pancreatic juice.3. In response to continuous secretin infusion, the preparation secreted for up to 6 hr a juice which was similar to that obtained in vivo, with the exception that the bicarbonate concentration decreased and the chloride concentration increased with time, even when the rate of secretion remained constant.4. The osmolalities of perfusate and secretion were identical over a range of 450 m-osmoles/kg, but the electrolyte concentration of the secretion was always slightly higher than that of the perfusate. Variations from perfusate isosmolality produced inverse changes in the secretion rate, over the range from 600 m-osmoles/kg, at which secretion ceased, to 150 m-osmoles/kg, at which the rate was highest. At perfusate osmolalities below 150 m-osmoles/kg secretion rapidly declined.5. Reduction in perfusate sodium chloride concentration, isosmolality being maintained with sucrose, caused a fall in secretion rate, but the sodium concentration of the juice remained constant until perfusate sodium concentration was reduced to about 70 m-equiv/l. Below this level it declined and sucrose was detected in the juice in quantities almost sufficient to account for the equiosmolality of juice and perfusate.6. Two hypotheses about the mechanism of water and electrolyte secretion by the pancreas are presented.

Prostaglandin action on pancreatic blood flow and on electrolyte and enzyme secretion by exocrine pancreas in vivo and in vitro

“…For in vitro experiments, the pancreas was isolated from anaesthetized cp'ts and perfused with a balanced salt solution as previously described (Case, Harper & Scratcherd, 1968). Prostaglandins were injected or infused into the arterial supply of the gland.…”

The Effects of Alloxanate, Nicotinic Acid and Imidazole on Secretory Processes and the Activities of Adenylate Cyclase and 3‘,5’‐amp Phosphodiesterase in Cat Pancreas

“…In order to stimulate purified beef heart phosphodiesterase with imidazole, Nair (1966) had to use concentrations of the order of 10-100 mm. Since addition of imidazole to the perfusate at such concentrations would be likely to cause inhibition by an osmotic effect (Case et al, 1968), in 4 experiments the effects of 100 mM imidazole addition were compared with the effects of adding an osmotically equivalent amount (50 mM) of sodium chloride. All experiments gave similar results; one is illustrated in Figure 3.…”

“…The standard perfusion fluid, isosmolal with cat plasma, had the following composition (mM): NaCl 125, KCI 4.3, NaHCO3 25, MgSO4 1.0, NaH2PO4 1.0, CaCl2 2.5 and glucose 5. Unless otherwise stated, drugs (nicotinic acid, alloxan (BDH, Chemicals Ltd.) and imidazole (Sigma Chemicals Ltd.)) were added to this perfusion fluid at concentrations of 3, 8 and 13 mM without compensatory reduction in NaCl concentration since osmotic changes of this magnitude have relatively little effect on secretory rate from this preparation (Case et al, 1968 (Lagerlof, 1942) or the method of Bernfield (1955); amylase activity is expressed as international units (iu).…”

“…Experiments were performed on a saline-perfused preparation of the cat's pancreas prepared, with slight modifications, as described in detail elsewhere (Case, Harper & Scratcherd, 1968). Briefly, the pancreas was surgically isolated from cats of either sex weighing 1-3.4 kg, which had been denied food 18 h before the experiment.…”

The effects of secretin, pancreozymin and acetylcholine on the concentration of adenosine 3′:5′-cyclic monophosphate in cat pancreas

“…The same result was obtained if pancreozymin infusion was superimposed on secretin infusion. The possibility that other organ systems caused these changes indirectly was eliminated by repeating the experiments with the perfused cat pancreas (Case, Harper & Scratcherd, 1968). Since vagal stimulation also causes enzyme secretion, close intra-arterial injections of acetylcholine were also tested.…”