The combination of the ionophore A23 187 and the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) stimulates amylase secretion from rabbit pancreatic acini up to a level equal to, or slightly higher than when carbachol is used as stimulant. Each of the two compounds alone gives only a minor stimulation. This synergistic effect of A23187 and TPA supports a role of protein kinase C in pancreatic enzyme secretion.

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SUMMARY1. The reflexion coefficients of a number of non-electrolytes and electrolytes have been determined in the isolated rabbit pancreas.2. The reflexion coefficients of the following non-electrolytes were: urea, -0-02; glycerol, 0-06; erythritol, 011; sorbitol, 0*41; mannitol, 0-42; arabinose, 0-72; xylose, 0-74, assuming a value of 1x00 for sucrose.3. These values are equal within the experimental error to values previously obtained with a tracer technique for the same preparation, but they are significantly lower than those reported by other investigators for the isolated perfused cat pancreas.4. Addition of 100 mM-sucrose to the bathing medium resulted in proportionally increased Na+ and K+ concentrations in the secreted fluid. The secreted fluid remained isotonic with the bathing medium under all circumstances.5. Addition of 10-5 M-carbachol to the bathing medium led to a reduction in the reflexion coefficient of sucrose from 1 to 0-85, but only when 25 mM-sucrose was used.6. The reflexion coefficients of electrolytes were: NaCl, 0 50; KCl, 0-51; NaHCO3, 0*52 and choline chloride, 1-02.7. It is concluded that the isolated rabbit pancreas is highly permeable, both to electrolytes and to small non-electrolytes, probably being more leaky than any other epithelium studied so far.

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