Interaction between doxorubicin and mitomycin C on mortality and myocardial contractility in guinea pig.

The present investigations were carried out in guinea pig to ascertain whether mitomycin C has a direct cardiotoxic effect or interacts with doxorubicin-induced cardiotoxicity. I.p. administration of mitomycin C did not modify the survival rate up to 30 days, whereas the combined administration of doxorubicin and mitomycin C significantly decreased the survival time in comparison to the doxorubicin-treated group. On isolated atria, mitomycin C did not cause significant inhibition of the contractile force or an enhancement of the doxorubicin-induced negative inotropic effect. These results do not support the possibility that mitomycin C potentiates the acute cardiotoxic effects produced by doxorubicin.