ABSTRACT
Isolated rabbit Clara cells and a transformed human bronchial epithelial cell line, BEAS-2B, were used to investigate the mechanism of cytotoxicity of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), a persistent insecticide and stable metabolite of 1,1,1-trichloro-2,2- bis(p-chlorophenyl)ethane. Both BEAS-2B cells and rabbit Clara cells were highly susceptible to DDD toxicity and were partially protected by 1-aminobenzotriazole, a suicide substrate inhibitor of cytochrome P450 enzymes. DDD (0.05 mM) killed 47 +/- 1.8% of rabbit Clara cells and 42 +/- 7.9% of BEAS-2B cells after 3 hr and 84 +/- 3.0% of rabbit Clara cells and 80 +/- 14% of BEAS-2B cells after 6 hr. Consequently, DDD is the most potent Clara cell toxicant recognized to date. The cytotoxicity of DDD to these cells was decreased by deuterium substitution at the C-1 position. Rabbit Clara cells and pulmonary microsomes incubated with 14C-DDD produced the fully oxidized acetic acid metabolite 2,2'-bis(p- chlorophenyl)acetic acid (DDA), but DDA was not formed by Clara cells when DDD was coincubated with 1-aminobenzotriazole. These results support the hypothesis that the cytotoxicity of DDD to susceptible subpopulations of rabbit and human lung cells is, at least in part, caused by cytochrome P450-mediated oxidation of DDD at C-1. A required step for the production of the cytotoxic intermediate is proposed to be the formation of a highly reactive acyl halide intermediate that is readily hydrolyzed to a stable, nontoxic metabolite, DDA.
Subject(s)
Dichlorodiphenyldichloroethane/pharmacokinetics , Dichlorodiphenyldichloroethane/toxicity , Lung/metabolism , Animals , Biotransformation , Bronchi/cytology , Bronchi/metabolism , Carbon Radioisotopes , Cell Line, Transformed , Cells, Cultured , DDT/analogs & derivatives , DDT/metabolism , DDT/toxicity , Deuterium , Epithelial Cells , Epithelium/metabolism , Humans , Kinetics , Lung/cytology , Microsomes/metabolism , Mitogens/metabolism , Mitogens/toxicity , Oxidation-Reduction , Rabbits , TritiumABSTRACT
Condensation of tetramethyl methylenebisphosphonate with 2,3-O-isopropylidene-5-O-trityl-D-ribose gave a mixture of 2,5-anhydro-1-deoxy-1-(diethoxyphosphinyl)-2,3 -O-isopropylidene-5-O-trityl-D-altritol and -allitol. Separation of the isomers and deprotection gave 2,5-anhydro-1-deoxy-1-phosphono-D-altritol and -allitol. The former is the stable isosteric methylenephosphonate analogue of alpha-D-ribose 1-phosphate, the ribose donor in nucleoside phosphorylase catalyzed nucleoside biosynthetic reactions. It did not, however, inhibit purine nucleoside phosphorylase at concentrations of 6 mM.