Activation of Secretagogue Independent Gastric Acid Secretion via Endothelial Nitric Oxide Synthase Stimulation in Rats

Background/Aims: L-arginine is an important mediator of cell division, wound healing, and immune function. It can be transformed by the nitric oxide synthase (NOS) to nitric oxide (NO), an important cell signaling molecule. Recent studies from our laboratory demonstrate specific effects of L-arginine (10mM) exposure on gastric acid secretion in rat parietal cells. Methods: Studies were performed with isolated gastric glands and the pH sensitive dye BCECF-AM +/- L-arginine to examine its effects on acid secretion. The direct NO-donor diethylamine NONOate sodium salt hydrate, was also used while monitoring intracellular pH. The specific inhibitor of the intracellular NO signal cascade ODQ was also used. Results: We found that gastric proton extrusion was activated with application of L-arginine (10mM), in a separate series when L-arginine (10mM) + L-NAME (30µM) were added there was no acid secretion. Addition of the NO-donor diethylamine NONOate sodium salt hydrate (10µM) also induced acid secretion. When the selective sGC-inhibitor ODQ was added with NONOate we did not observe acid secretion. Conclusion: We conclude that L-arginine is a novel secretagogue, which can mediate gastric acid secretion. Furthermore, the intake of L-arginine causes direct activation of the H + , K + ATPase and increased proton extrusion from parietal cells resulting in the increased risk for acid-related diseases. The NO/sGC/cGMP pathway has never been described as a possible intracellular mechanism for H + , K + ATPase activation before and presents a completely new scientific finding. Moreover, our studies demonstrate a novel role for L-NAME to effectively eliminate NOS induced acid secretion and thereby reducing the risk for L-arginine inducible ulcer disease.