Protective action of sulfur compounds against aldehyde toxicants of cigarette smoke

Acetaldehyde, acrolein, and formaldehyde are important toxicants of cigarette smoke. Since acetaldehyde is a toxicant common to both heavy alcohol drinking and heavy cigarette smoking, protection studies were undertaken in rats first against acetaldehyde lethality and later against acrolein and formaldehyde lethality. This paper summarizes findings from previously published studies. With acetaldehyde (LD 90 dose/72 hrs.) protection studies were carried out by pretreatment with a high oral dose (2 mmoles/kg) of L-cysteine and 17 other sulfur compounds. Good protection (80% or more survivors) was obtained with L-cysteine, N-acetylcysteine, thiamin . HCl, sodium metabisulfite, L-cysteic acid, and a combination (CTA) of L-cysteine, thiamin . HCl, and L-ascorbic acid. N-acetylcysteine, L-cysteic acid, and the combination CTA gave 100% protection (i.e. 100% survivors). With acrolein (LD 95 dose/72 hrs.), protection data showed 80% survivors with L-cysteine and 95% with the combination CTA. With formaldehyde (LD 95 dose/72 hrs.), protection resulted in 20% survivors with L-cysteine and 55% with the combination CTA. However, protection against formaldehyde lethality could be increased to 90% survivors by repeated dosing with L-ascorbic acid per se over a two day period prior to administration of formaldehyde. Further animal experimentation is necessary before any extrapolation of these findings for human use can be considered. Due to current interest, the potential value of N-acetylcysteine as a protectant is also discussed.