Acrylonitrile (AN) is a chemical widely used in the production of synthetic fibers, plastics and rubber. AN is a reactive chemical with an acute lethal action in experimental animals. Death in humans accidentally exposed to AN have been reported. Current industrial hygiene practices can limit the exposure of workers to AN during normal occupational procedures. However, accidental exposures to high levels can acutely affect the health of individuals involved in the production, transportation, and end use of AN. In the event of a large accidental release of AN, even the health of the general populace could be affected. AN can be oxidatively metabolized cyanide which is some ten times more toxic than the parent molecule on a molar basis. However, because of it high chemical reactivity with thiol groups in the body,the parent AN molecule is also thought to be toxic. Thus AN is a double edged sword and antidotal measures must take into account both the cyanide component and the """"""""other"""""""" component(s) of its toxic action. Unfortunately, the currently recommended antidotal therapy for AN poisoning focuses solely on the management of cyanide intoxication. Our objective is to mimic an acute dermal AN exposure and to measure the ability of thiol containing antidotes, e.g. N-acetyl-L- cysteine, to increase the clearance of acrylonitrile from the circulation. This will minimize the time available for AN to chemically react with protein thiol groups in vivo. Further we propose to ascertain whether the ability of N-acetyl-L-cysteine to decrease covalent binding, possibly by increasing AN clearance, is a direct effect of N-acetyl-L-cysteine or if it is acting indirectly through serving as a precursor for glutathione. In addition, we plan to use one and two dimensional gel electrophoresis to separate the specific tissue proteins to which AN is covalently bound and to use N-terminal sequencing of the blotted gels to identify these proteins. The ability of thiol containing antidotes to protect these proteins from AN covalent binding will be measured. Finally, we plan to use AN metabolite excretion patterns and the labeling by AN of specific amino acid sites in hemoglobin, as biomarkers for changes in AN disposition with increasing dose. Dispositional changes lead to a """"""""Trigger Point"""""""" above which lethality increases sharply with dose. The significance of this work is that we hope to gain some insight into the mechanism of action of N-acetyl-L-cysteine as AN antidote and to be able to understand, at the molecular level, the mechanisms involved in acute AN intoxication. Understanding the molecular basis for intoxication should allow us to design antidotes directed more specifically toward these mechanisms.
