['Arginine (Arg) is deficient in the serum of the preterm neonate and is lower in those developing intestinal ischemia. We investigated whether Arg or its precursor, citrulline (Cit), protects intestinal tight junctions (TJs) from hypoxia (HX) and determined whether inducible nitric oxide (NO) plays a role.', 'Neonatal piglet jejunal IPEC-J2 cell monolayers were treated with Arg or Cit, reversible and irreversible NO synthetase (NOS) inhibitors, and were exposed to HX. TJs were assessed by serial measurements of transepithelial electrical resistance (TEER), flux of inulin-fluorescein isothiocyanate, and immunofluorescent staining of TJ proteins.', 'We found that Arg and Cit were protective against HX-related damage. At the final time point (14\u2009h), the mean TEER ratio (TEER as compared with baseline) for Arg + HX and Cit + HX was significantly higher than that for HX alone. Both Arg and Cit were associated with decreased inulin flux across hypoxic monolayers and qualitatively preserved TJ proteins. Irreversible inhibition of NOS blocked this protective effect. Lipid peroxidation assay showed that our model did not produce oxidant injury.'] Do arginine and citrulline protect intestinal cell monolayer tight junctions from hypoxia-induced injury in piglets?