Human pharmacokinetics of the daunorubicin-DNA complex. An alternative view of the lysosomotropic theory

Serum and tissue concentrations of doxorubicin after IV administration of doxorubicin or doxorubicin-DNA complex to patients with gastrointestinal cancer

Blood and tissue concentrations of doxorubicin (DOX) were assayed after an intraoperative IV test dose of either free DOX 10 mg or its DNA complex 10 mg to patients with gastrointestinal cancer. After administration of the free drug, blood DOX levels decreased in an at least biphasic way, while DOX-DNA gave higher blood concentrations, which decreased slowly with no clear inflexion point on the concentration-time curve within the first hour. Tissue concentrations of DOX did not differ significantly after the two forms of the drug, liver being the tissue with the highest levels, followed by lymph node metastases, tumor tissue, muscle, and normal intestinal mucosa. If skeletal muscle can be used as a substitute for myocardium, lower cardiotoxicity of DOX-DNA than of DOX is not likely to be due to a difference in tissue uptake and retention between the two forms of DOX.

Toxic effects of free and DNA-linked daunorubicin on isolated rat cardiac myocytes

Isolated cardiac myocytes from adult rats were used as a model to study the cardiotoxicity of free and DNA-linked daunorubicin. The toxic effects on the myocytes were evaluated by studying morphological changes, trypan blue exclusion and cell membrane permeability to NADH, as determined by LDH-activity. At a concentration of 100 microM daunorubicin caused an increased plasma membrane permeability within 30 min. Using light microscopy, the myocytic injury induced by daunorubicin could be distinguished from that induced by anoxia or elevated pH. In contrast to the effect of the free drug, no toxic effects could be demonstrated after incubation with DNA-linked daunorubicin (100 microM) for 5 hours. The higher toxicity of the free drug was related to a much higher intracellular accumulation of daunorubicin. No fluorescent metabolites of daunorubicin could be detected in the myocardial cells. Daunorubicin did not induce lipid peroxidation, as judged by the absence of malondialdehyde production and evolution of ethane. It is concluded that daunorubicin exerts toxic effects on rat cardiac myocytes by mechanisms that do not involve lipid peroxidation. Isolated cardiac cells from adult rats seem to be a useful model for the further study of such mechanisms.