Houser S R, Burgis V, Martin F, Weinberg D
Am J Physiol. 1983 Jul;245(1):H90-7. doi: 10.1152/ajpheart.1983.245.1.H90.
The role of the Na-K pump in the control of cellular ion balance has long been appreciated. Recent studies suggest that the manner in which this ion transport system functions in hypertrophied failing (HF) cardiac muscle is markedly different from that seen in normal muscles. The ability of the sympathetic neurohormone, epinephrine, to modulate membrane potential changes thought to reflect the activity of the Na-K pump in normal and HF cardiac muscle was examined in this study. Specifically rate-related changes in membrane potential (Emax) thought to be associated with the Na-K pump were measured in intact functioning cat papillary muscles. The results of these studies demonstrate that the rate-related changes in Emax thought to be associated with Na-K activity were markedly altered in HF cardiac muscles. Emax in these muscles responded to periods of transient stimulation by first depolarizing and then slowly returning to a new steady state which was depolarized with respect to the initial predrive Emax. Emax in normal muscles also depolarized on drive, but returned to a new steady state more rapidly and eventually hyperpolarized. Epinephrine significantly affected these rate-related changes in Emax in normal muscles by causing all the rates of change in Emax to be increased. In HF muscles, on the other hand, epinephrine had no significant effect on these parameters at the concentration tested. These results suggest that under certain conditions HF cardiac muscle may be incapable of maintaining normal resting membrane potentials. In addition the modulating influence of epinephrine is markedly blunted.
钠钾泵在控制细胞离子平衡中的作用早已为人所知。最近的研究表明，这种离子转运系统在肥厚性衰竭（HF）心肌中的功能方式与正常肌肉中明显不同。本研究检测了交感神经激素肾上腺素调节膜电位变化的能力，该变化被认为反映了正常和HF心肌中钠钾泵的活性。具体而言，在完整功能的猫乳头肌中测量了被认为与钠钾泵相关的膜电位（Emax）的速率相关变化。这些研究结果表明，在HF心肌中，被认为与钠钾活性相关的Emax速率相关变化明显改变。这些肌肉中的Emax在短暂刺激期间首先去极化，然后缓慢回到一个新的稳定状态，相对于初始预驱动Emax，该状态是去极化的。正常肌肉中的Emax在驱动时也会去极化，但会更快地回到一个新的稳定状态，最终超极化。肾上腺素通过使Emax的所有变化速率增加，显著影响正常肌肉中Emax的这些速率相关变化。另一方面，在HF肌肉中，在所测试的浓度下，肾上腺素对这些参数没有显著影响。这些结果表明，在某些情况下，HF心肌可能无法维持正常的静息膜电位。此外，肾上腺素的调节作用明显减弱。
