Abdelmeguid A E, Feher J J
Department of Cardiology, Virginia Commonwealth University, Medical College of Virginia, Richmond 23298.
Circ Res. 1992 Nov;71(5):1049-58. doi: 10.1161/01.res.71.5.1049.
The effect of perfusate [Ca2+] on the function of cardiac sarcoplasmic reticulum (CSR) was assessed by the oxalate-supported Ca2+ uptake rate of ventricular homogenates of isolated rat hearts maintained in a modified Langendorff preparation. The total Ca2+ pumping activity of the CSR was determined by using 20 microM ruthenium red or 625 microM ryanodine to close the CSR Ca2+ release channel. The homogenate Ca2+ uptake rate in the absence of ruthenium red or ryanodine decreased progressively with increasing perfusate [Ca2+] (25.7 +/- 1.2, 21.4 +/- 1.5, 17.2 +/- 1.1, and 16.3 +/- 1.2 [mean +/- SEM] nmol Ca2+.min-1.mg-1 for hearts perfused for 5 minutes with 0.2, 1.4, 2.8, and 5.6 mM Ca2+, respectively; p = 0.0001; n = 8). This depression was not observed when Ca2+ uptake was assayed in the presence of ryanodine or ruthenium red. Since the Ca2+ uptake in the presence of ryanodine or ruthenium red is determined by the Ca(2+)-ATPase, this result suggests that perfusion with varying [Ca2+] did not affect the Ca(2+)-ATPase. The observed decrease in Ca2+ uptake in the absence of ryanodine or ruthenium red is caused by an increased efflux through the ryanodine-sensitive Ca2+ release channel. When hearts perfused for 5 minutes with 0.2 or 5.6 mM Ca2+ were reperfused for 10 minutes with 1.4 mM Ca2+, homogenate Ca2+ uptake rates were restored to near control levels. These effects of perfusate Ca2+ were not direct effects, because changes in the [Ca2+] of the homogenization medium did not alter the homogenate Ca2+ uptake activity in either the presence or absence of ryanodine. The homogenate Ca2+ uptake rates were unaffected by prior active loading of the CSR with Ca2+. These results suggest a regulatory role of perfusate Ca2+ in increasing the open state of the ryanodine-sensitive Ca2+ release channel that is distinct from the beat-to-beat regulation of Ca2+ release from the CSR by Ca2+ (Ca(2+)-induced Ca2+ release).
通过在改良Langendorff装置中维持的离体大鼠心脏心室匀浆的草酸盐支持的Ca2+摄取率，评估灌注液[Ca2+]对心肌肌浆网（CSR）功能的影响。使用20 microM钌红或625 microM兰尼碱封闭CSR Ca2+释放通道，测定CSR的总Ca2+泵浦活性。在不存在钌红或兰尼碱的情况下，匀浆Ca2+摄取率随着灌注液[Ca2+]的增加而逐渐降低（分别用0.2、1.4、2.8和5.6 mM Ca2+灌注5分钟的心脏，其摄取率为25.7±1.2、21.4±1.5、17.2±1.1和16.3±1.2[平均值±标准误]nmol Ca2+·min-1·mg-1；p = 0.0001；n = 8）。当在兰尼碱或钌红存在下测定Ca2+摄取时，未观察到这种降低。由于在兰尼碱或钌红存在下的Ca2+摄取由Ca(2+)-ATP酶决定，该结果表明用不同[Ca2+]灌注不影响Ca(2+)-ATP酶。在不存在兰尼碱或钌红的情况下观察到的Ca2+摄取降低是由通过兰尼碱敏感的Ca2+释放通道的外流增加引起的。当用0.2或5.6 mM Ca2+灌注5分钟的心脏再用1.4 mM Ca2+灌注10分钟时，匀浆Ca2+摄取率恢复到接近对照水平。灌注液Ca2+的这些作用不是直接作用，因为在存在或不存在兰尼碱的情况下，匀浆介质[Ca2+]的变化均未改变匀浆Ca2+摄取活性。匀浆Ca2+摄取率不受CSR预先用Ca2+主动加载的影响。这些结果表明灌注液Ca2+在增加兰尼碱敏感的Ca2+释放通道的开放状态方面具有调节作用，这与Ca2+对CSR Ca2+释放的逐搏调节（Ca(2+)-诱导的Ca2+释放）不同。
