Disposition of the pulmonary toxin, bleomycin

The disposition of bleomycin in rats was investigated with the use of a 57Co-labeled bleomycin radioimmunoassay. Bleomycin (1 mg/kg, ip) reached a peak serum level of 0.7-1.0 microgram/ml in 54 +/- 4 min (mean +/- SE) and was eliminated with a t 1/2 of 32 +/- 1 min. The apparent volume of distribution in rats was 184 +/- 11 ml/kg. No change in t 1/2 was observed when rats were pretreated with phenobarbital (1 mg/ml in drinking water for 4 days) or exposed to ozone (3 ppm, 24 hr). Probenecid (0.2 g/kg, ip) given 20 min prior to bleomycin administration increased the t 1/2 2-fold. The order of tissue distribution of 57Co-labeled bleomycin 2 hr after ip administration was: kidney greater than liver greater than lungs greater than spleen greater than heart greater than thymus. The affinity of 57Co-labeled bleomycin for homogenates of lungs, liver, or kidney was equal.