Selective iNOS inhibition enhances spontaneous gallbladder motility in the Australian possum

Gallbladder inflammation is a common and painful disease. Inducible nitric oxide synthase (iNOS) plays a major role in inflammatory diseases, and iNOS inhibitors are being developed as therapeutic agents. Reports are inconsistent regarding iNOS expression in normal gallbladder. The aim of this study was to determine the effect of iNOS inhibition on spontaneous gallbladder motility. mRNA extracted from normal possum gallbladders was analysed by PCR. Gallbladder contractility was evaluated using a highly selective iNOS inhibitor AR‐C102222AA (AR‐C) in in vitro muscle strips (0.1–10 000 μm) and in vivo (0.1–30 μmol kg−1) experiments. Gene expression analysis revealed the presence of iNOS mRNA in normal gallbladder (n = 3). In vitro, AR‐C (0.1–1000 μmol L−1) produced a concentration‐dependent increase in spontaneous gallbladder contractile activity and basal tension (P