OxyFile #234

Hydrogen peroxide-induced luminescence and evolution of 
molecular oxygen in human saliva.

Author:  Kou F; Takahama U

Source:  Arch Oral Biol 1995 Jan; 40(1):15-21


Low-level chemiluminescence (CL) appeared on addition of hydrogen 
peroxide to human saliva and then decayed slowly. Azide (10 
microM) inhibited CL by about 50% and deuterium oxide (99.75%) 
enhanced it about twofold. 1,4-Diazabicyclo[2,2,2]octane (50 mM) 
and tryptophan (10 mM) were also enhancing, which suggests that 
singlet oxygen participates in this CL. The optimal pH for CL was 
around 8.5. Molecular oxygen was produced on addition of hydrogen 
peroxide to human saliva with a time course similar to that of CL; 
the optimal pH for oxygen evolution was around 8.0. The levels of 
SCN- and OSCN- at first decreased and increased, respectively, on 
addition of hydrogen peroxide and then remained constant as long 
as the induced CL could be detected. Dithiothreitol (1 mM) and 
mercaptoethanol (1 mM) completely suppressed CL. Induced CL was 
observed in saliva dialysed against 10 mM sodium phosphate (pH 
7.5). Its intensity was increased by NaSCN, reaching a maximum 
around 0.1 mM NaSCN in the presence of 0.2 mM hydrogen peroxide. 
These results suggest that part of the molecular oxygen evolved on 
addition of hydrogen peroxide to human saliva is in a singlet 
state and that molecular oxygen is evolved by oxidation of 
hydrogen peroxide, which may be catalysed by OSCN- bound to 
salivary peroxidase.