Mechanism of methylene diphenyl diisocyanate glutathione conjugate micronuclei induction distinguishable from that of methylenedinaline.
Toxicologist 2000 Mar; 54(1):231
Methlyene di-phenyl diisocyanate (MDI) is widely used in the production of polyurethane products, such as wood binders and foams. Diisocyanates are very reactive compounds that can undergo nonenzymatic hydrolysis to form methylenedianiline (MDA), or react under physiological conditions with primary amines to form ureas and/or with thiols to form labile thiol acid esters. MDA is a carcinogen in animals and a suspected carcinogen in humans. We have previously reported that exposure of Brown Norway rats (BNR) to MDI induces micronuclei (MN) in bone marrow polychromatic erythrocytes. In vitro studies suggested that both MDI glutathione (MDI-GSH) conjugates and MDA are potential genotoxic metabolites of MDI. Addition of MDI directly to cell cultures did not induce micronuclei. The mechanism of micronuclei induction of these metabolites was explored in the present study. Chinese hamster lung fibroblasts were incubated with MDA or MDI-GSH. Micronuclei kinetichore from cytokinesis-blocked cells were labeled by immunofluorescent staining. Cells were washed, methanol fixed, treated with Tween 20 buffer, then labeled with antikineticore and fluoresceinated goat anti-human IgG antibodies to discern the presence of centromere within the micronuclei. Vincristine, DMSO and glutathone were used as positive, solvent and negative controls, respectively. MDA induced MN were negative with respect to anti-kineticore antibody binding. This is consistent with induction of chromosomal fragments by MDA binding to DNA. MDI-GSH induced MN had a significant increase in the number of anti-kineticore antibody labeled MN. MDI-GSH also increased the number of cells in metaphase. These results suggest that MDI-GSH MN induction was mediated through disruption of microtubules, whereas MDA MN induction was by a DNA-binding mechanism.
Physiological-factors; Physiological-effects; Thiols; Esters; Carcinogens; Laboratory-animals; Animals; Animal-studies; In-vitro-studies; Lung-disorders; Respiratory-system-disorders; Pulmonary-system-disorders
The Toxicologist. Society of Toxicology 39th Annual Meeting, March 19-23, 2000, Philadelphia, Pennsylvania