SECRETORY RESPONSES TO OUABAIN AND TO LOWERING Na⁺ IN THE ISOLATED PERFUSED PANCREAS OF THE GUINEA PIG

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Secretory responses to ouabain and to lowering extracellular Na⁺ concentration have been studied in the isolated perfused pancreas of guinea pig. Ouabain (1-100 μM) produced dose-dependent secretory responses (pancreatic juice flow and protein output). The responses to 10 μM ouabain were completely abolished in Ca²⁺ deficient environment. The peak level of juice flow induced by 10 or 100 μM ouabain was partly reduced but the protein output remained almost unchanged after atropinization (2 μM). Lowering extracellular Na⁺ concentration from control (156 mM) to 25, 50, or 100 mM induced the secretory responses. The responses to 25 mM Na⁺ were nullified after the removal of extracellular Ca²⁺. The responses were reduced to about one half after atropinization (2 μM). The present results are compatible with the view that the major portion of the secretory responses to ouabain and to low Na⁺ environment may be mediated by the release of acetylcholine and other peptidergic transmitters (possibly VIP and PHI) from the intrinsic nerve endings distributed to the exocrine pancreas of guinea pig.