The localization of a new antithrombotic agent, cilostazol, in CHO-K1 cells as demonstrated by autoradiography.

Cilostazol (6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)- qui nolinone, OPC-13013), a new antithrombotic agent, has a potent inhibitory action on platelet aggregation. The cellular and subcellular distribution of this compound was investigated. Autoradiographic studies using tritiated cilostazol showed that this compound penetrates the cell membrane of Chinese hamster ovary cells, clone K1 (CHO-K1 cells) and is distributed mainly in the cytoplasma. These results suggest that this compound exhibits its pharmacological action through specific inhibition of cytoplasmic cyclic AMP phosphodiesterase.