BLEACHED PIGMENT ACTIVATES TRANSDUCTION IN ISOLATED RODS OF THE SALAMANDER RETINA
BLEACHED PIGMENT ACTIVATES TRANSDUCTION IN ISOLATED RODS OF THE SALAMANDER RETINA
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DOI：
10.1113/jphysiol.1994.sp020358
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发表时间：
1994-10-15
影响因子：
5.5
通讯作者：
FAIN, GL
中科院分区：
文献类型：
--
作者：
CORNWALL, MC;FAIN, GL
1. 我们使用吸液电极记录技术，并快速将溶液切换为锂离子溶液和0.5毫摩尔的IBMX溶液，以估算蝾螈（Ambystoma tigrinum）分离视杆细胞中鸟苷酸磷酸二酯酶（PDE）和鸟苷酸环化酶的反应速率。
2. 我们发现，稳定的背景光会加速PDE和环化酶的反应速度。这两种酶的稳定反应速度似乎是背景光强度的饱和函数。
3. 漂白也会加速PDE和环化酶的反应。这种效应在漂白刺激去除后很长时间内（长达2小时）仍能维持，只有当光色素通过外源性生色团再生时才会逆转。
4. 估算的PDE和环化酶的稳态反应速度似乎是色素漂白量的线性函数，就好像每个漂白的色素分子以相同的概率和增益激活转导级联反应。
5. 漂白色素激活转导的效率仅为激活视紫红质（Rh*）的10⁻⁶到10⁻⁷倍，但在大量漂白后，这足以产生视杆细胞的“等效背景”激发，这可能至少在一定程度上是漂白脱敏的原因。
1. We have used suction electrode recording together with rapid steps into Li+ solution and 0.5 mM IBMX solution to estimate the rates of the guanylyl phosphodiesterase (PDE) and guanylyl cyclase in isolated rods of the salamander, Ambystoma tigrinum.2. We show that both the PDE and cyclase velocities are accelerated by steady background light. The steady velocities of both enzymes appear to be saturating functions of background intensity.3. Bleaching also accelerates both the PDE and cyclase. This effect is maintained long after the bleaching stimulus is removed (up to 2 h) and is reversed only if the photopigment is regenerated with exogenous chromophore.4. The estimated steady-state PDE and cyclase velocities appear to be linear functions of the amount of pigment bleached, as if each bleached pigment molecule activated the transduction cascade with the same probability and gain.5. The effectiveness of bleached pigment in activating transduction is only 10(-6) to 10(-7) times that of activated rhodopsin (Rh*), but this is sufficient after large bleaches to produce an 'equivalent background' excitation of the rod, which is probably responsible, at least in part, for bleaching desensitization.