32P-postlabeling analysis of DNA adducts formed in vitro and in rat skin by methylenediphenyl-4,4'-diisocyanate (MDI).
The 32P-postlabeling method was adapted for the detection of DNA adducts formed by methylenediphenyl-4,4'-diisocyanate (MDI). Incubation of the 3'-phosphates of the deoxyribosides of cytosine (C), adenine (A), guanine (G) and thymine (T) with MDI in Tris buffer resulted in the formation of 5, 7, 8, and 2 reaction products, respectively. Incubation of DNA with MDI resulted in detectable levels of 5, 2, and 1 adducts attributable to C, A, and G. Analysis of DNA isolated from the epidermis of rats treated dermally with 9 mg MDI showed an adduct pattern similar to the one seen in the in vitro DNA incubation. A total adduct level of 7 per 10(8) nucleotides was measured, the limit of detection was 2 adducts per 10(10) nucleotides. The data indicate that a minute fraction of MDI can reach DNA in vivo in a chemically reactive form. In comparison with the genotoxic skin carcinogen 7,12-dimethylbenz[a]anthracene on the other hand, the DNA-binding potency of MDI was more than 1000-fold lower.
Vock
E H
EH
Institute of Toxicology, Swiss Federal Institute of Technology, Schwerzenbach.
Cantoreggi
S
S
Gupta
R C
RC
Lutz
W K
WK
D000818:Animals; D001345:Autoradiography; D018736:DNA Adducts / Q000032:analysis*; D005260:Female; D066298:In Vitro Techniques; D017953:Isocyanates / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000378:metabolism*; D001559:Benzhydryl Compounds
D018736:DNA Adducts; D017953:Isocyanates; D010761:Phosphorus Radioisotopes; C005969:4,4'-diphenylmethane diisocyanate; D001559:Benzhydryl Compounds