Pancreatic secretion in vitro in "Cl–-free," "CO2-free," and low-Na+ environment

Abstract

Pancreatic secretion from the rabbit pancreas in vitro was not maintained in "Cl^–-free," "CO₂-free," or low-Na⁺ environments. When the missing ion was added to the bath, secretion recovered. Results show that "primary" HCO₃^– secretion need not be "isotonic" and that a HCO₃^–-Cl^– exchange mechanism may not be of major importance in producing a secretion of variable electrolyte composition. There was an interdependence of Cl^– and HCO₃^– output, suggesting that these ions are not secreted by independent mechanisms. HCO₃^– output in the absence of an exogenous CO₂ source was about 10% of control values. Na⁺ and Cl^–, as well as HCO₃^–, may be secreted primarily transcellularly. A "unicellular" model of pancreatic secretion based on the active secretion of Na⁺ and accumulation of K⁺ by the secreting pancreatic cell is presented.