Hahin R
Biological Sciences Department, Northern Illinois University, Dekalb 06115.
J Membr Biol. 1990 Dec;118(3):233-42. doi: 10.1007/BF01868607.
Delays in the development of activation of Na currents were studied using voltage-clamped frog skeletal muscle fibers. Na currents elicited by a depolarizing voltage step from a hyperpolarized membrane potential were delayed in their activation when compared to Na currents elicited from the resting potential. The magnitude of the delay increased with larger hyperpolarizing potentials and decreased with larger depolarizing test potentials. Delays in activation observed following chloramine-T treatment that partially removes inactivation did not differ from delays observed before treatment. Longer exposures of the muscle fiber to chloramine-T led to a complete loss of inactivation, coincident with an elimination of the hyperpolarization-induced delays in activation. Steady-state slow inactivation was virtually unaffected by prolonged exposures of the fibers to chloramine-T that eliminated fast inactivation. The results show that chloramine-T acts at a number of sites to alter both activation and inactivation. Markov model simulations of the results show that chloramine-T alters fundamental time constants of the system by altering both activation and inactivation rate constants.
利用电压钳制的青蛙骨骼肌纤维研究了钠电流激活的延迟情况。与从静息电位引发的钠电流相比，由超极化膜电位的去极化电压阶跃引发的钠电流在激活时出现延迟。延迟的幅度随着超极化电位增大而增加，随着去极化测试电位增大而减小。在氯胺-T处理部分消除失活后观察到的激活延迟与处理前观察到的延迟没有差异。肌肉纤维长时间暴露于氯胺-T会导致完全丧失失活，同时消除超极化诱导的激活延迟。纤维长时间暴露于氯胺-T消除快速失活后，稳态慢失活实际上未受影响。结果表明，氯胺-T作用于多个位点以改变激活和失活。对结果的马尔可夫模型模拟表明，氯胺-T通过改变激活和失活速率常数来改变系统的基本时间常数。
