ABSTRACT
Doxorubicin is an important anthracycline which has proven anticancer activity. However its clinical use has been limited by its cardiotoxicity. Many studies have been conducted to explore the mechanism of this untoward effect, but have given conflicting data. This study has been conducted to determine the role of calcium in this regard. Langendroff's technique was used. The data obtained from a significant number of rabbits shows that Doxorubicin suppresses the inotropic activity of heart significantly [p<0.01] while; it does not alter the chronotropic activity significantly [p<0.01] in lower doses, but reduces this activity significantly [p<0.01] at higher doses of calcium. The result clearly supports, the Ca[++] mediated cardio toxic mechanism of heart