TOXIC EFFECTS OF ANTIMALARIAL-DRUGS IN PARAMECIUM - ROLE OF CALCIUM CHANNELS

The antimalarial drugs, quinacrine, quinine and mefloquine, as well as the structurally-similar compound, W-7, inhibit calcium-dependent bac kward swimming and calcium currents in Paramecium calkinsi. These drug s are also toxic to paramecia at high concentrations. Therefore, one s ite of toxic action of the drugs may be the calcium channel. To test t his hypothesis, the toxicity of the antimalarials and W-7 was compared in paramecia with and without calcium channels. Since calcium channel s are located on the cilia, calcium channels were removed from the par amecia by deciliating the cells. Deciliated cells were found to be les s susceptible to the lethal effects of the antimalarials and W-7 than their ciliated counterparts. Moreover, Pawns, mutants of P. tetraureli a that possess cilia but lack functional calcium channels, were also l ess susceptible to the antimalarials than wild-type cells. Thus, calci um channels may be one site of toxic action of the antimalarial drugs in paramecia and perhaps in other protists.