Plasma and pulmonary pharmacokinetics of bleomycin in murine strains that are sensitive and resistant to bleomycin-induced pulmonary fibrosis

Previous studies have shown that C57Bl/6N mice are sensitive and BALB/c mice are resistant to the pulmonary fibrotic effects of bleomycin (BLM). We assessed the plasma elimination and pulmonary content of BLM in C57Bl/6N and BALB/c mice treated with a single dose of 3H]BLM (80 mg/kg i.v.) to determine whether these murine strains show corresponding differences in BLM pharmacokinetics and pulmonary disposition after systemic administration of the drug. Serial blood samples were obtained from each animal and lungs were collected after pulmonary lavage or vascular perfusion with saline. Administration of BLM (80 mg/kg i.v.) produced significant elevations in lung hydroxyproline (35%) in C57Bl/6N but not in BALB/c mice. In contrast, BALB/c mice were more sensitive to pulmonary fibrosis induced with cyclophosphamide (200 mg/kg i.p.) compared to C57Bl/6N mice, indicating that strain sensitivity to pulmonary fibrosis is drug specific in these mice. BLM showed first order plasma elimination kinetics over 30 min in both strains with a shorter half-life in the sensitive strain (9.6 +/- 0.3 min in C57Bl/6N vs. 12.7 +/- 1.9 min in BALB/c). Plasma elimination deviated from first order kinetics after 30 min in both strains and plasma levels of BLM were up to 2-fold higher in the resistant strain over a 3-hr time course. Radioactivity in saline-perfused lungs was also significantly higher (1.5-2-fold) in BALB/c mice for least 1 hr after BLM injection. A similar fraction of the total lung radioactivity (approximately 80%) was recovered from both strains by pulmonary lavage, suggesting that BLM enters the alveolar spaces relatively freely in each strain.(ABSTRACT TRUNCATED AT 250 WORDS)