Picones A, Korenbrot J I
Department of Physiology, University of California Medical School, San Francisco 94143.
Biophys J. 1994 Feb;66(2 Pt 1):360-5. doi: 10.1016/s0006-3495(94)80785-4.
We measured cGMP-dependent currents, under voltage clamp, in membrane patches detached from the outer segment of single-cone photoreceptors isolated from the retina of striped bass. We analyzed the variance of the current about its mean and the spectral density distribution of the current fluctuations. From the analysis of variance, we determined that the cGMP-gated channels increase their probability of opening with increasing cGMP up to a maximum value of 0.87 +/- 0.03. The dependence on cGMP of the probability of opening is well described by a Hill equation with Km = 60.2 +/- 3.7 microM and n = 2.33 +/- 0.32 at -50 mV. At the same voltage, the spectral density distribution is well fit by the sum of two Lorentzians with corner frequencies at 26 +/- 18 and 318 +/- 58 Hz. The single-channel conductance calculated from the current noise by two different methods suggests that the most frequently occupied conductance state has an amplitude of about 18 pS.
我们在电压钳制条件下，测量了从条纹鲈视网膜分离出的单个视锥光感受器外段上膜片的环鸟苷酸（cGMP）依赖性电流。我们分析了电流围绕其均值的方差以及电流波动的功率谱密度分布。通过方差分析，我们确定cGMP门控通道随着cGMP浓度增加其开放概率也增加，直至最大值0.87±0.03。在-50 mV时，开放概率对cGMP的依赖性通过希尔方程很好地描述，其中Km = 60.2±3.7 microM，n = 2.33±0.32。在相同电压下，功率谱密度分布通过两个角频率分别为26±18和318±58 Hz的洛伦兹曲线之和得到很好的拟合。通过两种不同方法从电流噪声计算出的单通道电导表明，最常占据的电导状态幅度约为18 pS。
