In vitro effects of toxaphene on mitochondrial calcium ATPase and calcium uptake in selected rat tissues

In vitro effects of toxaphene on Ca 2+-ATPase activity and 45Ca 2+-uptake were studied in mitochondrial fractions of heart, kidney and liver tissues of rat. Mitochondrial fractions were prepared by the conventional centrifugation method. Ca 2+-ATPase activity was determined by measuring the inorganic phosphate liberated during ATP hydrolysis. Toxaphene inhibited Ca 2+-ATPase in a concentration dependent manner in all the three tissues. Substrate activation kinetics, with heart, kidney and liver tissue fractions, revealed that toxaphene inhibited Ca 2+-ATPase activity non-competetively by decreasing the maximum velocity of the enzyme without affecting the enzyme-substrate affinity. Toxaphene also inhibited mitochondrial 45Ca 2+-uptake in the three selected tissues in a concentration dependent manner. These results indicate that toxaphene is an inhibitor of mitochondrial Ca 2+-ATPase and calcium transport in heart, kidney and liver tissues of rat.