RUTHENIUM RED REDUCES THE CA2-RETICULUM( SENSITIVITY OF CA2+ UPTAKE INTO CARDIAC SARCOPLASMIC)

Ruthenium red inhibits mitochondrial Ca2+ uptake and is widely used as an inhibitor of ryanodine-sensitive Ca2+ channels that function to re lease Ca2+ from the sarcoplasmic reticulum (SR) of muscle cells. It al so has effects on other Ca2+ channels and ion transporters. To study t he effects of ruthenium red on Ca2+ transport into the SR of cardiac m uscle cells, fluorescence measurements of Ca2+ uptake into cardiac SR vesicles were made. Ruthenium red significantly decreased the Ca2+ sen sitivity of SR uptake in a dose-dependent manner at concentrations ran ging from 5 mu M to 20 mu M. Then were no significant effects of ruthe nium red on the maximum velocity or the Hill coefficient of SR Ca2+ up take.