Potentiating effect of daunorubicin on vasocontractile responses to KCl and BAY K 8644 in rat aorta.

The effects of daunorubicin on vasoconstraction by several agonists have been investigated on isolated aortic strips from rats. Pretreatment of the strips with daunorubicin (17.7 microM) potentiated the contractile response to low concentrations of KCl or to BAY K 8644 but not to phenylephrine or clonidine. The maximal contractile response to KCl was not affected by the pretreatment while that to BAY K 8644 was increased. The potentiated response to KCl could be eliminated by addition of nifedipine (1 microM) or use of a calcium-free solution. The maximal contractile response to BAY K 8644 was greatly increased by partial depolarization with KCl (10 mM, final concn) in the control solution but only slightly increased by the partial depolarization in the solution with daunorubicin. These results suggest that daunorubicin facilitates activation of the voltage-dependent calcium channel and increases the contractile responses to KCl and BAY K 8644 in rat aorta.