DETERMINATION OF PEPLOMYCIN IN MOUSE-TISSUES AND BIOFLUIDS BY RADIOIMMUNOASSAY

Peplomycin, an antitumour antibiotic analogue of bleomycin, was measur ed in mouse tissues using a rapid radioimmunoassay. Antiserum, obtaine d by immunizing rabbits with peplomycin-bovine serum albumin conjugate , showed no significant cross-reactivity with the closely related pepl omycin analogues bleomycin and liblomycin, nor with a number of other structurally unrelated antitumour drugs. The assay is sensitive and ca n detect peplomycin levels as low as 2 ng ml-1. The relative intra- an d inter-assay standard deviation is less-than-or-equal-to 5%, indicati ng good assay reproducibility. Peplomycin levels in mouse tissues were easily determined without extraction. Fifteen minutes after administr ation of a single intraperitoneal dose of peplomycin at 8.5 mg kg-1 (1 /10 of LD50), high drug levels were found in plasma (46 mug ml-1), kid neys (38 mug g-1), urine and bladder (32 mug ml-1), followed by gastro intestinal tract (13 mug g-1), lung (8 mug g-1), spleen (3.7 mug g-1), heart (3.6 mug g-1), gall bladder (2.7 mug g-1), liver (2 mug g-1), a nd brain (0.6 mug g-1). The total amount of drug in all these organs a ccounted for more than 80% of the dose administered. We conclude that the radioimmunoassay is sensitive and reproducibile and is an ideal to ol for measuring peplomycin in tissues and biofluids for pharmacologic al studies.