Photoresponse of the Vertebrate Sphincter Pupillae

当可见光照射到许多脊椎动物的虹膜上时，它们的平滑肌肉括约肌就会收缩。它们的作用光谱与视紫红质的吸收光谱类似，视紫红质是视网膜视杆细胞色素。这不是由神经元件或甚至细胞膜上的任何电事件来调节的。有人建议确定心肌细胞是否含有视紫红质以及其他各种可能参与光转导和调节平滑肌收缩的蛋白质，包括：转导蛋白，一种杆状蛋白，以及三种常见于平滑肌收缩装置的蛋白质：钙调蛋白、肌球蛋白轻链激酶和肌球蛋白。已经推导出了被认为涉及的生化反应的数学描述，该项目建议通过各种细胞生理学技术来检验该理论的预测。这些措施包括使细胞对原本不能通过细胞膜的分子具有很强的渗透性。通过这种方式，可以通过实验来设定分子的浓度。另一种要使用的技术是通过强烈的闪光从不耐光的络合物中释放出具有生物活性的化合物。光直接激活青蛙虹膜肌肉涉及一系列生化反应，这些反应将感光色素的漂白与以肌动蛋白-肌球蛋白为基础的系统收缩的平滑肌结合在一起。这些生化反应参与了多种细胞类型的信号转导。因此，对这一独特系统的进一步研究可能有助于从总体上揭示信号转导机制。

The smooth muscle sphincters of the irises of many vertebrate species contract when visible light is shined on them. They do so with an action spectrum like the absorption spectrum of rhodopsin, the retinal rod pigment. This is not mediated by neural elements or even any electrical event at the cell membrane. It is proposed to determine whether the myocytes contain rhodopsin as well as various other proteins suspected of being involved, in phototransduction and regulation of smooth muscle contraction including: transducin, a rod protein, and three proteins commonly found in the contractile apparatus of smooth muscle; calmodulin, myosin light chain kinase and myosin. A mathematical description of the biochemical reactions thought to be involved has been derived and this project proposes to test the predictions of the theory by a variety of cellular physiological techniques. These would include making the cells very permeable to molecules which otherwise would not pass the cell membrane. In this way the concentrations of molecules can be set experimentally. Another technique to be used is to release biologically active compounds from photolabile complexes by strong flashes of light. The direct activation of the frog iris muscle by light involves a combination of biochemical reactions that couple the bleaching of a photopigment to contraction of the smooth muscle by an actin-myosin based system. These biochemical reactions are involved in signal transduction in a variety of cell types. Thus, further study of this unique system may shed new light on signal transduction mechanisms in general.