Rapundalo S T, Briggs F N, Feher J J
J Mol Cell Cardiol. 1986 Aug;18(8):837-51. doi: 10.1016/s0022-2828(86)80958-0.
Normothermic global ischemia of 7, 10, 15 and 60 min was found to depress oxalate supported calcium uptake rate measured either in unfractionated homogenates or isolated sarcoplasmic reticulum. The degree of depression increased with the duration of ischemia. Comparison of the isolated sarcoplasmic reticulum with unfractionated homogenates showed that the isolated sarcoplasmic reticulum was more damaged by ischemia than the unfractionated homogenate. The cause of this discrepancy was not due to inactivation of sarcoplasmic reticulum during isolation but was due to the discard of greater portions of undamaged sarcoplasmic reticulum as the ischemic period increased. Ischemia preferentially affected that sarcoplasmic reticulum most easily fragmented by homogenization. To determine if the depression of sarcoplasmic reticulum function is uniform throughout the isolated fraction, we compared several properties of the isolated fractions. After 10 min of ischemia, extensive properties such as calcium oxalate uptake rate, calcium ATPase rate, calcium oxalate capacity and steady-state calcium loading were depressed 50, 41, 48 and 24% respectively. In contrast, intensive properties such as permeability, calcium-ATPase turnover rate, and ratio of forward nucleotide flux to reverse nucleotide flux were unaffected by ischemia. However, one intensive property, the coupling ratio, was depressed 20%. We conclude from this difference in the effects of ischemia on extensive and intensive properties that the major effect of ischemia is to inactivate the Ca-ATPase.
研究发现，7分钟、10分钟、15分钟和60分钟的常温性全脑缺血会降低未分级匀浆或分离的肌浆网中草酸盐支持的钙摄取率。抑制程度随缺血持续时间增加。将分离的肌浆网与未分级匀浆进行比较表明，分离的肌浆网比未分级匀浆更容易受到缺血损伤。这种差异的原因不是由于分离过程中肌浆网失活，而是由于随着缺血时间延长，更多未受损的肌浆网被丢弃。缺血优先影响匀浆时最易破碎的肌浆网。为了确定肌浆网功能的抑制在整个分离部分是否一致，我们比较了分离部分的几个特性。缺血10分钟后，草酸盐钙摄取率、钙ATP酶速率、草酸盐钙容量和稳态钙负荷等广泛特性分别降低了50%、41%、48%和24%。相比之下，渗透率、钙-ATP酶周转率以及正向核苷酸通量与反向核苷酸通量之比等强度特性不受缺血影响。然而，一个强度特性，即偶联率，降低了20%。从缺血对广泛特性和强度特性影响的这种差异中，我们得出结论，缺血的主要作用是使钙ATP酶失活。
