Wang S Q, Feng Q, Zhou Z Q
College of Life Sciences, Peking University, Beijing.
Sheng Li Xue Bao. 1995 Dec;47(6):551-8.
The force-interval and force-frequency relationships and the effects of Cd2+ and ryanodine on the myocardial action potential and contraction were compared between hibernating (HGS) and active (AGS) ground squirrels Citellus dauricus. (1) Raising the driving frequency caused a negative inotropic effect in the AGS group, but a biphasic change with an increase of the peak force followed by a decrease in the HGS group. The contraction in HGS group exhibited a more pronounced post-interval potentiation, and was more significantly modulated by the driving frequency. (2) HGS animals displaged action potentials of shorter early-stage duration and stronger contractions of shorter time course in comparison with the AGS animals. Both the action potential and the contraction of HGS group were less affected by Cd2+, but the contraction was more significantly inhibited by ryanodine than that of the AGS group. Our results suggested that dependence of cardiac excitation-contraction coupling on calcium influx was weakened, while the function of sarcoplasmic reticulum as a source of activator Ca2+ was enhanced during hibernation, which might take an important part in the cold-tolerant adaptation of hibernating hearts.
比较了冬眠地松鼠（HGS）和活动地松鼠（AGS）的心肌动作电位和收缩过程中的力-间隔和力-频率关系，以及Cd2+和雷诺丁对它们的影响。（1）提高驱动频率在AGS组中引起负性肌力作用，但在HGS组中呈双相变化，即峰值力先增加后降低。HGS组的收缩表现出更明显的间隔后增强，并且受驱动频率的调节更显著。（2）与AGS动物相比，HGS动物的动作电位早期时程较短，收缩的时程较短且更强。HGS组的动作电位和收缩受Cd2+的影响较小，但收缩受雷诺丁的抑制比AGS组更显著。我们的结果表明，冬眠期间心脏兴奋-收缩偶联对钙内流的依赖性减弱，而肌浆网作为激活剂Ca2+来源的功能增强，这可能在冬眠心脏的耐寒适应中起重要作用。
