Effect of (2"R)-4'-O-tetrahydropyranyladriamycin, a new antitumor antibiotic, on the bone marrow function of rabbits. (1) Intravenous administration by a single bolus injection

New Zealand White rabbits were treated with (2"R)-4'-O-tetrahydropyranyladriamycin-HCl (THP), a new antitumor antibiotic, by an intravenous bolus injection at a dose of 1, 2 or 4 mg/kg. The peripheral leucocyte counts decreased markedly at doses of 2 and 4 mg/kg 1 to 7 days after injection, and the lymphocytes and neutrophils were affected. The nucleated cell count decreased in the bone marrow. Especially 3 days after injection, remarkable reductions of erythroids and immatured myelocytes were observed, with a subsequent rise of the matured myelocytes ratio in bone marrow cell constituents. These changes resulted in a marked increase of M/E ratio. Doxorubicin also showed an inhibitory effect on the bone marrow function of rabbits but the effect was slightly lower than THP. These changes of bone marrow cells reverted 7 days after injection and the recovery of the reduced peripheral leucocyte was also observed 14 days after injection. Therefore, it can be concluded that THP showed suppressive but reversible effects on the bone marrow function of rabbits.