HYDROGEN PEROXIDE-INDUCED LUMINESCENCE AND EVOLUTION OF MOLECULAR-OXYGEN IN HUMAN SALIVA

Low-level chemiluminescence (CL) appeared on addition of hydrogen pero xide to human saliva and then decayed slowly. Azide (10 mu M) inhibite d CL by about 50% and deuterium oxide (99.75%) enhanced it about twofo ld. 1,4-Diazabicyclo[2,2,2]octane (50 mM) and tryptophan (10 mM) were also enhancing, which suggests that singlet oxygen participates in thi s CL. The optimal pH for CL was around 8.5. Molecular oxygen was produ ced on addition of hydrogen peroxide to human saliva with a time cours e similar to that of CL; the optimal pH for oxygen evolution was aroun d 8.0. The levels of SCN- and OSCN- at first decreased and increased, respectively, on addition of hydrogen peroxide and then remained const ant as long as the induced CL could be detected. Dithiothreitol (1 mM) and mercaptoethanol (1 mM) completely suppressed CL. Induced CL was o bserved in saliva dialysed against 10 mM sodium phosphate (pH 7.5). It s intensity was increased by NaSCN, reaching a maximum around 0.1 mM N aSCN in the presence of 0.2 mM hydrogen peroxide. These results sugges t that part of the molecular oxygen evolved on addition of hydrogen pe roxide to human saliva is in a singlet slate acid that molecular oxyge n is evolved by oxidation of hydrogen peroxide, which may be catalysed by OSCN- bound to salivary peroxidase.