PLASMA-MEMBRANE CALCIUM FLUXES IN INTACT RODS ARE INCONSISTENT WITH THE CALCIUM HYPOTHESIS
PLASMA-MEMBRANE CALCIUM FLUXES IN INTACT RODS ARE INCONSISTENT WITH THE CALCIUM HYPOTHESIS
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DOI：
10.1073/pnas.83.4.1150
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发表时间：
1986-02-01
影响因子：
11.1
通讯作者：
GOLD, GH
中科院分区：
文献类型：
--
作者：
GOLD, GH
研究了细胞外杆光电压和光诱导穿过杆质膜的净 Ca 通量之间的时间关系。净 Ca 通量测量值源自离体牛蛙视网膜受体表面的细胞外 Ca 浓度测量值。如前所述，光照导致 Ca 净流出，随后发生净流入，在此期间释放的 Ca 被回收。然而，净 Ca 通量有两个特征与细胞内游离 Ca 是视杆细胞光转导的细胞内信使的假设不一致。首先，在维持光电压饱和期间，净 Ca 流出是瞬态的，随着与刺激强度和持续时间无关的刻板时间过程下降。其次，Ca 吸收过程中净流入的显着速率与光电压波形没有相关性。这些观察结果与“Ca假说”不一致。相反，这些数据证实了最近的发现，表明光会导致细胞内游离 Ca 浓度降低而不是增加。
The temporal relationship between the extracellular rod photovoltage and light-induced net Ca fluxes across the rod plasma membrane is investigated. The net Ca flux measurements are derived from extracellular Ca concentration measurements at the receptor surface of the isolated bullfrog retina. As reported previously, illumination leads to a net Ca efflux, which is followed by a net influx, during which the released Ca is taken back up. However, the net Ca flux has two characteristics that are inconsistent with the hypothesis that intracellular free Ca is the intracellular messenger for phototransduction in rods. First, during maintained photovoltage saturation, the net Ca efflux is transient, declining with a stereotypic time course that is independent of stimulus intensity and duration. Second, the significant rate of net influx during Ca uptake has no correlate in the photovoltage waveform. These observations are not consistent with the "Ca hypothesis". Rather, these data corroborate recent findings suggesting that light causes a decrease rather than an increase in intracellular free Ca concentration.