Tumorigenicity of the optical enantiomers of the diastereomeric benzo[a]pyrene 7,8-diol-9,10-epoxides in newborn mice: exceptional activity of (+)-7beta,8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene.

The tumorigenicities of benzo[a]pyrene and each optical enantiomer of the diastereomeric benzo[a]pyrene 7,8-diol-9,10-epoxides derived from trans-7,8-dihydroxy-7,8-dihydrobenzol[a]pyrene were tested by sequential intraperitoneal injection of mice with 1,2, and 4 nmol, or with 2, 4, and 8 nmol of each compound on the 1st, 8th, and 15th day of life, respectively. The experiment was terminated when the animals were 34--37 weeks old. (+)-7beta, 8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzol[a]pyrene [(+)-BP-7beta,8alpha-diol-9alpha,10alpha-epoxide 2] had exceptional tumorigenicity, whereas benzo[a]-pyrene and the other three optically pure isomers of the benzo[a]pyrene 7,8-diol,9,10-epoxides had little or no activity. These results demonstrate differences in the carcinogenic activities of optically active isomers of a polycyclic hydrocarbon diol epoxide. Eleven percent of control mice had pulmonary tumors, whereas 71% and 100% of the mice treated with a total dose of 7 or 14 nmol of (+)-BP-7beta,8alpha-diol-9alpha,10alpha-epoxide 2, respectively, had pulmonary tumors. Control mice had an average of 0.12 pulmonary tumors per mouse, whereas mice treated with a total dose of 7 or 14 nmol of (+)-BP-7beta,8alpha-diol-9alpha,10alpha-epoxide 2 had 1.72 and 7.67 pulmonary tumors per mouse, respectively. Mice treated with 14 nmol of (-)-BP-7alpha,8beta-diol-9beta,10beta-epoxide 2, (-)-BP-7beta,8alpha-diol-9beta,10beta-epoxide 1, or (+)-BP-7alpha,8beta-diol-9alpha,10alpha-epoxide 1 had 0.13, 0.25, and 0.34 pulmonary tumors per animal, respectively.