Seleno compounds such as selenocystamine and seleno-D, L-cystine were found to catalyze the decomposition of S-nitrosothiols (e.g. S-nitroso-glutathione and S-nitroso-N-acetyl-D, L-penicillamine) in the presence of different thiols (e.g. glutathione,N-acetyl-D-peniciliamine and 2-mercaptoethanol), and liberate nitric oxide. It was also found that glutathione peroxidase itself can catalyze the decomposition of S-nitrosoglutathione without the presence of any thiol or H2O2. (C) 1996 Academic Press, Inc.