8-Br-cGMP和cGMP对蟾蜍视杆光敏感通道作用的比较研究

A COMPARATIVE STUDY OF THE ACTION OF 8-Br-cGMP AND cGMP ON THE LIGHT-SENSITIVE CHANNEL IN TOAD RODS

在蟾蜍视网膜的视杆外段上进行片膜钳记录.在同一片膜中,8-Br-cGMP开启的通道,似乎是cGMP所开启的同一光敏感通道.在相同的片膜电位下,由同一片膜诱发同样大小的膜电流,所灌流的8-Br-cGMP溶液的浓度要大大低于cGMP溶液的浓度.再者,8-Br-cGMP被磷酸二酯酸水解的速率,比cGMP的要慢得多.结果表明,在开启视杆外段的光敏感通道的过程中,cGMP分子中的3＇,5＇-环一磷酸可能起主要作用.

Patch-clamp recordings were made from rod outer segments (ROS) of toad retina. 8-Br-cGMP opened a channel that appeared to be the same as light-sensitive channel, which was opened by cGMP from the same patch. Under the same patch membrane potential, 8-Br-cGMP also caused membrane current to increase to about the same magnitude from the same patch as did cGMP. However, the 8-Br-cGMP concentration was much lower than the cGMP concentration. Moreover, the rate which 8-Br-cGMP was hydrolyzed by phosphodiesterase is much more slowly than that cGMP did. The results suggest that 3', 5'-cyclic monophoshate of cGMP molecule plays an important role in opening the light-sensitive channel of ROS.