The products of the reaction between toluene diisocyanate and water contract isolated guinea pig bronchi.

We have investigated the ability of the products of the reaction between toluene diisocyanate (TDI) and water to contract bronchial smooth muscle. The experiments were performed in isolated guinea pig bronchi. TDI, both 2,4- and 2,6-toluenediamine (TDA) and mixtures of 2,4- and 2,6-TDA (ratio 80:20 and 20:80) caused concentration-dependent contraction in the isolated bronchi. The mixture of disubstituted urea and biuret also contracted the bronchi, but not in a concentration-dependent fashion. Our results provide evidence that all products of the reaction between toluene diisocyanate and water have the ability to contract isolated bronchial smooth muscle in guinea pigs. Whatever the role of toluenediamine in the adverse respiratory effects induced by exposure to isocyanates, our findings reveal the necessity of in vivo studies on the metabolism of inhaled toluene diisocyanate in humans to improve our understanding of the mechanism of action of isocyanates.