Aryl hydrocarbon hydroxylase induction in rat pulmonary alveolar macrophages (PAMs) by diesel particulates and their extracts.

The Aryl hydrocarbon hydroxylase (AHH) activity in the lavaged PAMs was investigated in male Fischer rats after inhalation of diluted diesel exhaust (DE), and compared with intratracheal instillation of the organic solvent extract of hydrocarbons adsorbed on the particulate surface. Animals were exposed to concentrations of 1500 micrograms/m3 or 6000 micrograms/m3 of diesel particulates, 20 hrs/day, 7 days/wk for 2 days up to 28 days, or treated with a single intratracheal dose of DE extract or benzo[a]pyrene (B[a]P) dissolved in gelatin-saline solution. The counts of lavageable PAM and polymorphonuclear leukocytes (PMN) were significantly elevated in the exposed rats. However, a decrease of AHH activity was found in the PAM cells after four weeks of exposure to both particulate concentrations. The AHH activity in the PAMs from rats injected intratracheally with 5 mg/kg of B[a]P was slightly increased; no change was observed in PAMs similarly treated with DE extract. Enzyme induction is not noted because of absence of sufficient quantities of hydrocarbons need for induction. This could be further potentiated that macrophages metabolize and perhaps reduce hydrocarbon levels by translocation.