Cyclic GMP-activated channels of salamander retinal rods: spatial distribution and variation of responsiveness.
Cyclic GMP-activated channels of salamander retinal rods: spatial distribution and variation of responsiveness.
复制标题
蝾螈视网膜杆的循环 GMP 激活通道：空间分布和反应性变化。
DOI：
10.1113/jphysiol.1992.sp019040
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Baylor,DA
中科院分区：
文献类型：
--
作者：
Karpen,JW;Loney,DA;Baylor,DA
1.采用膜片钳技术研究了蝾螈视杆细胞外节表面膜环鸟苷酸激活通道的面密度和空间位置。2.从外节切除的斑块中活性通道（即能够响应环GMP的通道）的密度由活性通道的数量N和膜面积A确定。N估计从饱和浓度的环GMP诱导的电流，而A估计从贴片的电容。3.在从41个在光照下制备的孤立外节切除的贴片中，活性通道密度在显著范围内变化：0.34 - 629微米2，平均值为166微米2。密度与斑块面积在此或任何研究的条件。4.通过用松散贴片电极记录不同位置处的局部暗电流来测量换能杆外段上开放通道的空间分布。开放通道的表观密度在外部段的圆周周围以及其长度上下仅变化约+/-50%。这表明，切除的斑块中的宽范围密度不是由于对通道的非均匀空间分布进行采样而产生的。5.从十六个具有健康外观和正常大小的饱和光响应的暗适应全细胞切下的贴片具有1.1 - 200微米-2的活性通道密度，平均值为60微米-2。来自20个光适应的全细胞的斑块具有相似的密度。来自整个细胞的许多密度远低于预期。这一点，以及密度的广泛变化，表明获得贴片通常会降低活性通道的密度。在一个补丁的通道的数量是相当稳定的，从1秒到30分钟后切除，排除渐进变性或吸附的通道的玻璃作为这种效果的原因。6.在外部溶液中存在钙的情况下，从全细胞切下的贴片中的平均活性通道密度低于不存在钙的情况（80与152微米-2，分别为n = 36和30）。7.我们得出结论，通道蛋白的拷贝以至少650微米2的密度存在于外节的表面膜中，并且通道的分布在1微米尺度上相当均匀。（400字处截断摘要）
1. Patch‐clamp methods were used to investigate the areal density and spatial location of cyclic GMP‐activated channels in the surface membrane of salamander rod outer segments. 2. The density of active channels (i.e. channels able to respond to cyclic GMP) in patches excised from outer segments was determined from the number of active channels, N, and the membrane area, A. N was estimated from the current induced by a saturating concentration of cyclic GMP, while A was estimated from the electrical capacitance of the patch. 3. In patches excised from forty‐one isolated outer segments prepared in the light the active channel density varied over a remarkable range: 0.34‐629 microns‐2, with a mean of 166 microns‐2. Density was not correlated with patch area in this or any of the conditions studied. 4. The spatial distribution of open channels on the outer segment of a transducing rod was measured by recording the local dark current at various positions with a loose‐patch electrode. The apparent density of open channels varied by only about +/‐ 50% around the circumference of the outer segment and up and down its length. This indicates that the wide range of densities in excised patches did not result from sampling a non‐uniform spatial distribution of channels. 5. Patches excised from sixteen dark‐adapted whole cells with healthy appearances and saturating light responses of normal size had active channel densities of 1.1‐200 microns‐2, with a mean of 60 microns‐2. Patches from twenty light‐adapted whole cells had similar densities. Many densities from the whole cells were much lower than expected. This, and the wide variation in densities, suggests that obtaining a patch often lowered the density of active channels. The number of channels in a patch was quite stable from 1 s to 30 min after excision, ruling out progressive denaturation or adsorption of channels to the glass as a cause for this effect. 6. The mean active channel density in patches excised from whole cells was lower with calcium present in the external solution than with calcium absent (80 vs. 152 microns‐2, n = 36 and 30 respectively). 7. We conclude that copies of the channel protein were present at a density of at least 650 microns‐2 in the surface membrane of the outer segment and that the distribution of channels was fairly uniform on a 1 micron scale.(ABSTRACT TRUNCATED AT 400 WORDS)