Induction of Transient Cell Proliferation by Manufactured Gas Plant Residue in B6C3F₁ male mice

Fifteen day old B6C3F1 male mice were exposed by intraperitoneal (IP) injection to a Maximally Tolerated Dose of Manufactured Gas Plant (MGP) residue (1:32 dilution in DMSO or 1:8 in com oil), 375 μg total of benzo[alpyrene in DMSO or com oil (CO) or DMSO and CO vehicle alone. On days 2, 4 and 7 post-treatment mice were injected IP with bromodeoxyuridine (BRdU) at a concentration of 50 μg/g of weight 1 hour prior to euthanasia. Immunoperoxidase staining for BRdU was performed and mitotic index (MI) determined for target tissues: bronchial mucosa, forestomach and liver. In MGP-exposed mice, MI in bronchial mucosa was increased 842% with DMSO vehicle and 555% in CO vehicle at day 2, MI was increased in forestomach mucosa by 40% at day 4 and MI was increased in liver by 50% at day 7 compared to controls. Therefore, complex mixtures such as MGP residue are capable of inducing transient cell proliferation.