Calcium channel blockers verapamil and diltiazem impaired rubratoxin B-caused toxicity in HL60 cells

The effects of calcium channel blockers (CCBs) verapamil and diltiazem on t he toxicity of rubratoxin B in HL60 cells were investigated. Treatment of r ubratoxin B caused a considerable rate of blebbing. fragmentation and conde nsation of cells. The rate of this morphological change was much lower in t he concomitant rubratoxin B and CCBs-treated cells than in the cells treate d only with rubratoxin B. Cell viability was determined by measuring mitoch ondrial succinic dehydrogenase activity and the rare of cell proliferation. The results of these assays were of the same tendency as that of the morph ological study. CCBs attenuated rubratoxin B's toxicity on cell viability b ecause of their protective action. Rubratoxin B induced apoptosis in the pr esence of internucleosomal fragmentation. In contrast, concomitant rubratox in B and CCBs treatment did not. Taken together, the above results indicate d that CCBs impaired the toxicity including morphological change, cell viab ility and apoptosis caused by rubratoxin B. (C) 2000 Elsevier Science Irela nd Ltd. All rights reserved.