Effects of alloxan and streptozotocin on calcium transport in isolated mouse liver mitochondria

Abstract The effect of alloxan and streptozotocin on the fluxes of Ca 2+ in isolated mouse liver mitochondria was studied with dual wave-length spectrophotometry, using antipyrylazo III as metallochromic indicator. Streptozotocin had no effect on Ca 2+ uptake, whereas alloxan inhibited the initial rate and extent of Ca 2+ influx in a way dependent on the duration of preincubation, and occurence of Pi in the reaction mixture. A rapid release of Ca 2+ followed upon addition of either FCCP or alloxan after the reaction had been started. When added to preloaded mitochondria, alloxan induced a concentration dependent release of Ca 2+ . The data suggest that alloxan induces an initial release of mitochondrial Ca 2+ , which is followed by inhibition of Ca 2+ influx. The initial release may be due to uncoupler activity induced by alloxan, and the inhibition of Ca 2+ influx may be a consequence of inhibited Pi transport.