Effects of doxorubicin and its aglycone metabolite on calcium sequestration by rabbit heart, liver, and kidney mitochondria

Previous investigators have shown that following doxorubicin treatment heart mitochondria appear swollen and contain intramitochondrial dense inclusion bodies identified as calcium phosphate. In vitro studies have shown that similar morphological changes occur in mitochondria previously loaded with excess calcium. The present studies were performed to determine the effects of doxorubicin and its aglycone metabolite on ⁴⁵Ca²⁺ uptake by mitochondria isolated from the heart, liver, and kidney of the rabbit. Doxorubicin (100 μM) significantly inhibited the initial rate of ⁴⁵Ca²⁺ accumulated by mitochondria isolated from the three tissues. In contrast, the aglycone metabolite (100 μM) induced the reverse effect. In preloaded mitochondria the aglycone stimulated the release of calcium while doxorubicin was without effect. Mitochondria from the heart were significantly more sensitive to the effects of these anthracyclines than were mitochondria from the other two tissues. If these in vitro effects also occur in vitro, then the aglycone metabolite would be a more likely candidate in explaining the morphological changes in heart mitochondria previously described.