Effect of intravenous infusion of hypertonic glucose solutions on pancreatic HCO3 secretion

To examine why intravenous infusion of hypertonic non-electrolyte solutions inhibit pancreatic HCO₃^- secretion, the relationship between pancreatic HCO₃^- secretion and plasma pH was examined before and following intravenous infusion of hypertonic glucose to 5 anesthetized, secretin infused (2.7 C.U./kg b. wt. h^-1) pigs. Hyperglycemia (plasma glucose 103±6 mmol/l) did not significantly change plasma pH, NaM⁺, K⁺, Cl^- and HCO₃^- concentrations. Hyperglycemia reduced pancreatic water flux by 48±5% and raised pancreatic juice HCO₃^- concentration by 43±4 mmol/l. Concurrently, HCO₃^- secretion fell by 34±5%. Acidosis, produced through intravenous HC1 infusion and CO₂ addition to inspired air, reduced HCO₃^- secretion by 40±6 ±mol/min and 30±5 ±mol/min per 0.1 pH unit reduction in plasma pH before and during hyperglycemia, respectively, and abolished HCO₃ secretion at an estimated plasma pH of 6.51 ±0.06 before and a pH of 6.63±0.05 during hyperglycemia. We conclude that hypertonic glucose infusions inhibit pancreatic water flux and cause an increase in pancreatic juice HCO₃^- concentration which may inhibit HCO₃^- secretion through an effect on acid-base balance in secretory cells.