Fesenko E E, Kolesnikov S S, Lyubarsky A L
Biochim Biophys Acta. 1986 Apr 25;856(3):661-71. doi: 10.1016/0005-2736(86)90162-8.
In order to identify the intracellular transmitter in the phototransduction process in the retinal rod, the action of cGMP, 2',3'cGMP, cAMP, GMP and Ca2+ on the isolated inside-out patches of the plasma membrane of retinal rods of the frog (Rana temporaria) was studied. cGMP applied at the intracellular membrane surface markedly increased the conductance of patches. The action of cGMP took place in the absence of nucleoside triphosphates and, hence, was not mediated by protein phosphorylation. The dependence of cGMP-induced component of conductance on cGMP concentration was S-shaped, with half-saturation within 10-30 microM and a Hill coefficient of about 1.7-1.8. cAMP, 2',3'cGMP, GMP (1 mM) did not exhibit any action on the membrane. Ca2+ did not affect the patch conductance in the absence of cGMP. In the presence of cGMP, lowering Ca2+ concentration from 10(-3) to 10(-8) M decreased the cGMP-dependent component of conductance by 20-30%. The approximate value of the elementary event underlying the cGMP-induced conductance estimated from the magnitude of the variance of the cGMP-induced current is within 100-250 fS. We suppose that the cGMP-activated channels found by us provide the light-sensitive conductance of the rod plasma membrane in vivo and that cGMP is the intracellular transmitter acting in the phototransduction process.
为了确定视网膜视杆细胞光转导过程中的细胞内递质，研究了环鸟苷酸（cGMP）、2',3'-环鸟苷酸、环腺苷酸（cAMP）、鸟苷酸（GMP）和钙离子（Ca2+）对青蛙（林蛙）视网膜视杆细胞质膜分离的内向外膜片的作用。在细胞内膜表面施加cGMP可显著增加膜片的电导。cGMP的作用在没有核苷三磷酸的情况下发生，因此不是由蛋白质磷酸化介导的。cGMP诱导的电导成分对cGMP浓度的依赖性呈S形，半饱和浓度在10-30微摩尔范围内，希尔系数约为1.7-1.8。cAMP、2',3'-环鸟苷酸、GMP（1毫摩尔）对膜没有任何作用。在没有cGMP的情况下，Ca2+不影响膜片电导。在有cGMP的情况下，将Ca2+浓度从10^(-3)降至10^(-8)摩尔可使cGMP依赖性电导成分降低20-30%。根据cGMP诱导电流的方差大小估计，cGMP诱导电导的基本事件的近似值在100-250飞西门子范围内。我们推测，我们发现的cGMP激活通道在体内提供了视杆细胞质膜的光敏感电导，并且cGMP是在光转导过程中起作用的细胞内递质。
