Wang Shi Qiang, Lakatta Edward G, Cheng Heping, Zhou Zeng Quan
National Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China.
J Exp Biol. 2002 Oct;205(Pt 19):2957-62. doi: 10.1242/jeb.205.19.2957.
Intracellular Ca(2+) homeostasis is a prerequisite for a healthy cell life. While cells from some mammals may suffer dysregulation of intracellular Ca(2+) levels under certain deleterious and stressful conditions, including hypothermia and ischemia, cells from mammalian hibernators exhibit a remarkable ability to maintain a homeostatic intracellular Ca(2+) environment. Compared with cells from non-hibernators, hibernator cells are characterized by downregulation of the activity of Ca(2+) channels in the cell membrane, which helps to prevent excessive Ca(2+) entry. Concomitantly, sequestration of Ca(2+) by intracellular Ca(2+) stores, especially the sarcoplasmic/endoplasmic reticulum, is enhanced to keep the resting levels of intracellular Ca(2+) stable. An increase in stored Ca(2+) in heart cells during hibernation ensures that the levels of Ca(2+) messenger are sufficient for forceful cell contraction under conditions of hypothermia. Maintenance of Na(+) gradients, via Na(+)-Ca(2+) exchangers, is also important in the Ca(2+) homeostasis of hibernator cells. Understanding the adaptive mechanisms of Ca(2+) regulation in hibernating mammals may suggest new strategies to protect nonhibernator cells, including those of humans, from Ca(2+)-induced dysfunction.
细胞内钙离子稳态是细胞健康生存的前提条件。虽然在某些有害和应激条件下，如体温过低和局部缺血时，一些哺乳动物的细胞可能会出现细胞内钙离子水平失调的情况，但哺乳动物冬眠动物的细胞表现出显著的能力来维持细胞内钙离子的稳态环境。与非冬眠动物的细胞相比，冬眠动物的细胞其细胞膜上钙离子通道活性下调，这有助于防止过多的钙离子进入。与此同时，细胞内钙离子储存库，尤其是肌浆网/内质网对钙离子的隔离作用增强，以保持细胞内钙离子的静息水平稳定。冬眠期间心脏细胞中储存的钙离子增加，确保了在体温过低的情况下，钙离子信使水平足以支持细胞有力收缩。通过钠钙交换体维持钠离子梯度，对冬眠动物细胞的钙离子稳态也很重要。了解冬眠哺乳动物钙离子调节的适应性机制，可能会为保护非冬眠动物细胞（包括人类细胞）免受钙离子诱导的功能障碍提供新策略。
