Brown J E, Rubin L J, Ghalayini A J, Tarver A P, Irvine R F, Berridge M J, Anderson R E
Nature. 1984;311(5982):160-3. doi: 10.1038/311160a0.
Photoreceptor excitation begins with the absorption of a photon by rhodopsin and proceeds through an unknown sequence of steps that leads to changes in specific ionic conductances. These conductance changes produce the receptor potential. It has been proposed that hydrolysis of phosphoinositides is involved in the control of a variety of physiological processes. Recent studies have implicated inositol 1,4,5-trisphosphate as an intracellular messenger in the cascade mediating hormone-stimulated secretion. We propose that one of the steps in the excitatory cascade in Limulus ventral photoreceptors may be an increase in intracellular concentration of myo-inositol polyphosphates, derived from hydrolysis of the membrane component phosphatidylinositol bisphosphate by a phospholipase. Here we present biochemical and electrophysiological evidence that an inositol polyphosphate may be an intracellular messenger in the cascade mediating excitation, based on the following criteria: the cells possess the synthetic and degradative metabolism for the messenger; the natural stimulus leads to a change in the concentration of the messenger within the cells; and intracellular injection of exogenous messenger mimics naturally occurring electrophysiological events.
光感受器的兴奋始于视紫红质吸收一个光子，并通过一系列未知步骤进行，这些步骤导致特定离子电导的变化。这些电导变化产生感受器电位。有人提出磷酸肌醇的水解参与多种生理过程的控制。最近的研究表明，肌醇1,4,5 -三磷酸作为细胞内信使参与介导激素刺激分泌的级联反应。我们提出，鲎腹侧光感受器兴奋级联反应中的一个步骤可能是肌醇多磷酸的细胞内浓度增加，它源自膜成分磷脂酰肌醇二磷酸被磷脂酶水解。在此，我们基于以下标准，提供生化和电生理证据，证明肌醇多磷酸可能是介导兴奋的级联反应中的细胞内信使：细胞具有该信使的合成和降解代谢；自然刺激导致细胞内信使浓度发生变化；细胞内注射外源性信使可模拟自然发生的电生理事件。
