Inhibition by Sr2+ of specific mitochondrial Ca2+-efflux pathways.
The effect of Sr2+ on the set point for external Ca2+ was studied in rat heart and liver mitochondria with the aid of a Ca2+-sensitive electrode. In respiring mitochondria the set point is determined by the rates of Ca2+ influx on the Ca2+ uniporter and efflux by various mechanisms. We studied the Ca2+-Na+ exchange pathway in heart mitochondria and the delta psi-modulated efflux pathway in liver mitochondria. Prior accumulation of Sr2+ was found to shift the set points towards lower external Ca2+ both in heart mitochondria under conditions of Ca2+-Na+ exchange and in liver mitochondria under conditions that should promote opening of the delta psi-modulated pathway. The effect on the set point was found to be due to inhibition of Ca2+ efflux by Sr2+ taken up by the mitochondria, while Sr2+ efflux was too slow to be measurable.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D012430:Ruthenium Red / Q000494:pharmacology; D013324:Strontium / Q000494:pharmacology*
D007473:Ion Channels; D012430:Ruthenium Red; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D002118:Calcium; D013324:Strontium