A study on urinary thioethers by detecting N-acetylcysteine and thiophenol after alkaline hydrolysis

A method is described for the selective determination of thiol compounds liberated by alkaline hydrolysis of urine. It is based on the procedure described by Newton et al. Two thiol compounds were detected selectively: N-acetylcysteine and thiophenol. The following results were obtained: 1. On alkaline hydrolysis (at room temperature) among other thiols N-acetylcysteine is released. The amount of NAC increases after administration to rats of compounds, which directly or after metabolisation are bound by glutathione conjugation, such as diethylmaleate. 2. In these cases the amount of total thiols and NAC released by alkaline hydrolysis are closely related to each other. 3. Monitoring urines of smokers and non-smokers revealed a significant difference between non-smokers and smokers of the released NAC. So it may be concluded that exposure to certain electrophilic agents reacting with GSH increases the NAC as well as total thiols detected after alkaline hydrolysis of urine. 2. On alkaline hydrolysis (at 95 degrees C) thiophenol can be detected. Evidence is presented that thiophenol is derived from the benzene metabolite S-phenyl-N-acetyl-cysteine: 1. after treatment with radioactive benzene of rats the peak of the thiophenol-derivative elutes together with a radioactive peak; 2. inhalation of benzene increases the peak of the thiophenol-derivative in the urine of a human volunteer. 3. The amount of thiophenol detected by the described method in the urines of smokers is increased in comparison to non-smokers. This is in accordance with the observation that the benzene concentration is elevated in the blood of smokers.