Summary: A simple photometric procedure was developed for the determination of thiocyanate (SCN~) in plasma and saliva without deproteinisation or dialysis. Fe(III) ions form a red coloured complex with SCNw ith a inaximum absorbance at 460 nm. Mercury(II) nitrate is used to run a sample blank. A manual and an automated Version (COBAS ΒΙΟ) of the method is described. The method is linear up to 5000 μηιοΐ/ΐ SCN~. The CV of the between^run precision is 2.8 -8% for the manual and 2.6 -6.6% for the automated method. The SCN~ plasma concentration was 21 -134 μιηοΐ/l in nonsmokers and 44-260 μιηοΐ/ΐ in smokers. In mixed saliva, the concentration is much higher than in plasma: 1.57-5.5 mmol/1 in smokers and 0.79 -3.9 mmol/1 in nonsmokers. Plasma* but not oral fluid SCN~, is a valuable parameter for studying smoking habits in population surveys. Mowever, its use is limited. In our experience only heavy smokers can be distinguished from nonsmokers.
Nitrite was formed on incubation of N-nitrosamines with a reconstituted monooxygenase system, consisting of cytochrome P-450 (P-450) and NADPH P-450 reductase from pig liver. Nitrite was not obtained when the nitrosamines were incubated with NADPH P-450 reductase alone or when molecular oxygen or NADPH were omitted. Interaction of nitrosamines with the reconstituted P-450 system or with hemoglobin under reducing conditions resulted in optical spectra identical with those obtained with nitrite. It is proposed that N-nitrosamines are denitrosated by electron transfer from the hemoprotein iron to the nitrosamine molecule.
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