Comparative measurement of cyanide and paraquat mitochondrial toxicity using two different mitochondrial toxicity assays.

ABSTRACT Cyanide (KCN) and paraquat (PQ) are very toxic to mitochondria. In this study the toxicity of KCN and PQ in the isolated rat liver mitochondria was determined using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and JG-B (Janus green B) assay by multiwell scanning spectrophotometry. JG-B was used not only for the vital staining of mitochondria, but also for the mitochondrial viability assay and was compared to the MTT assay. The rat liver mitochondria were first isolated by centrifuge in a mixture of 0.25 M saccharose solution and 0.05 M Tris buffer. Various concentrations of paraquat (0.001 to 100 mM) and KCN (0.0001 to 100 M) on the mitochondria isolated from the liver were investigated. The 50% lethal concentration of toxins were found for PQ (4.45 +/- 0.02, 4.96 +/- 0.01) and KCN (0.22 +/- 0.02, 0.49 +/- 0.02), as determined by these assays ( JG-B and MTT, respectively ). Significant correlations were also observed among the two methods with a 95% coefficient interval (r(2) = 0.84, p < 0.001; r(2) = 0.91, p < 0.001; PQ and KCN, respectively). These results suggest that both methods are reliable and are comparable for determining the mitochondrial assay. It is concluded that the JG-B assay may be preferable to the MTT assay because of its simplicity, low cost, sensitivity, and objectivity; in addition, this method is not time dependent.