| A role for gene variants in regulating the pharmacokinetics of systemically available toxicants has not yet been established. A panel of 18 genetically-diverse inbred mouse strains was used to determine the range of total exposure kinetic parameters in blood and bone marrow following a single oral administration of benzene (100 microg/kg) to male and female mice. Large ranges in several pharmacokinetic parameters were found when data from blood and bone marrow were analyzed. AUC and CL_F pharmacokinetic parameters in blood and bone marrow pharmacokinetics were strikingly different as were these parameters in males and females. Final clearance (CL_F) was found to be the most statistically robust pharmacokinetic parameter as it accounted for exposure of the matrix (AUC) and normalized for dose variations among the strains. The CL_F values in blood and bone marrow used for haplotype association mapping showed 331 and 164 quantitative trait loci with statistical significance, respectively (male mice; -logP>4). Two loci were found to be shared between males and females QTL bone marrow data sets and one common locus was found for male blood and bone marrow data. No overlap was found among blood QTL in males and females (or between blood and bone marrow data from females). Protein and mRNA expression data for the primary benzene-metabolizing enzymes CYP2E1 and UGT1A6 showed very little strain-dependent variation. Strain-dependent differences in mRNA levels of NQO1 and MPO were small but statistically significant, as were those for GAPDH and beta2-microglobulin. These data demonstrated that polymorphisms with the greatest contribution toward overall variations in systemic exposures occurred in genes encoding for non-metabolic proteins. While exposure does not equate to toxicity, identification of the genes regulating distribution and clearance may be useful for investigating host susceptibility to toxic effects following benzene exposure. This research was supported in part by the NIEHS NTP Grant N01ES45529, NIEHS Toxicology and Toxicogenomics Training Grant (5T32ES007091-29), NIEHS/NTP Division of Intramural Research, and Southwest Environmental Science Center Grant P3ES06694. |
