Zhou Z Q, Liu B, Dryden W F, Wang L C
Department of Biology, Peking University, Beijing, People's Republic of China.
Am J Physiol. 1991 Feb;260(2 Pt 2):R353-8. doi: 10.1152/ajpregu.1991.260.2.R353.
The cardiac mechanical restitution was compared in papillary muscles between the active and the hibernating Richardson's ground squirrels at 0.1, 2.8, and 5 mM external Ca2+ concentration [( Ca2+]o). The amplitude of the restitution was significantly higher in hibernating animals between 37 and 7 degrees C at all [Ca2+]o. The first postrest contraction (F1) was highest at 20 degrees C and lower at 37 and 7 degrees C in both groups. The pause duration for maximum F1 was 30 s in active but 10 s in hibernating animals at 37 degrees C and increased to 100 s in both groups at 7 degrees C. The postrest potentiation was eliminated by 10(-6) M ryanodine at 20 degrees C in both groups, and this inhibitory effect was more pronounced in the hibernating group. Together, our results suggest that the activator Ca2+ for excitation-contraction coupling is mainly derived from the sarcoplasmic reticulum (SR) pool in both active and hibernating ground squirrel, and the dependence on SR Ca2+ release via ryanodine-sensitive Ca2+ channels is more marked in the hibernating state. Furthermore, there is no significant difference in sensitivity of the cardiac mechanical restitution to [Ca2+]o between the active and the hibernating condition.
在0.1、2.8和5 mM的细胞外Ca2+浓度（[Ca2+]o）下，比较了活跃状态和冬眠状态的北美 Richardson 地松鼠乳头肌的心脏机械恢复情况。在所有[Ca2+]o条件下，冬眠动物在37℃至7℃之间恢复的幅度显著更高。两组中，首次复跳后收缩（F1）在20℃时最高，在37℃和7℃时较低。在37℃时，活跃动物达到最大F1的暂停持续时间为30秒，而冬眠动物为10秒；在7℃时，两组均增加到100秒。在20℃时，两组的复跳后增强均被10(-6) M 兰尼碱消除，且这种抑制作用在冬眠组中更明显。总之，我们的结果表明，在活跃和冬眠的地松鼠中，兴奋 - 收缩偶联的激活剂Ca2+主要来源于肌浆网（SR）池，并且冬眠状态下对通过兰尼碱敏感Ca2+通道释放的SR Ca2+的依赖性更明显。此外，活跃状态和冬眠状态下心脏机械恢复对[Ca2+]o的敏感性没有显著差异。
