Demontis G C, Ratto G M, Bisti S, Cervetto L
Istituto Policattedra di Discipline Biologiche, Università di Pisa, Italy.
Biophys J. 1995 Aug;69(2):439-50. doi: 10.1016/S0006-3495(95)79917-9.
Membrane current and light response were recorded from rods of monkey and guinea pig by means of suction electrodes. The correlation between adaptation and the Na+/K+ pump was investigated by measuring light-dependent changes in sensitivity with and without inhibition of Na+/K+ ATPase by strophanthidin. Strophanthidin was found to reduce the dark current, to slow the time course of the photoresponse, and to increase light sensitivity. At concentrations between 20 and 500 nM, the pump inhibitor suppressed in a reversible way the current re-activation occurring during prolonged illumination and modified the light-dependent decrease in sensitivity, which in control conditions approximates to a Weber-Fechner function. The effects of the pump inhibitor on the adaptive properties of rods are associated with an increased time constant of the membrane current attributed to the operation of the Na+:Ca2+,K+ exchanger. The effects of rapid application of the pump inhibitor on the current re-activation are consistent with the idea that significant changes in the internal sodium occur in rods of mammals during background illumination and that they play an important role in the process of light adaptation.
通过吸力电极记录了猴和豚鼠视杆细胞的膜电流和光反应。通过测量在有无毒毛花苷抑制Na⁺/K⁺ ATP酶的情况下光依赖性敏感性变化，研究了适应性与Na⁺/K⁺泵之间的相关性。发现毒毛花苷可降低暗电流，减慢光反应的时间进程，并增加光敏感性。在20至500 nM的浓度范围内，泵抑制剂以可逆方式抑制长时间光照期间发生的电流重新激活，并改变光依赖性敏感性降低，在对照条件下，这种降低近似于韦伯-费希纳函数。泵抑制剂对视杆细胞适应性特性的影响与归因于Na⁺:Ca²⁺,K⁺交换器运作的膜电流时间常数增加有关。泵抑制剂快速应用对电流重新激活的影响与以下观点一致，即在背景光照期间哺乳动物视杆细胞内钠发生显著变化，并且它们在光适应过程中起重要作用。
