Basic Research of Light-Evoked Changes in the Interphotoreceptor Matrix

(1)光敏间受体基质（interphotoreceptor matrix， IPM）在绿光和蓝光适应型大鼠中存在光诱发变化，而在红光适应型大鼠中未发现。结果表明，杆状光感受器在IPM的光诱发变化中起主要作用。(2)电镜观察发现，暗适应大鼠视网膜外节周围弥漫性地可见到IPM颗粒成分，而光适应大鼠视网膜色素上皮的顶突上可见到IPM颗粒成分的积累。光诱发的IPM变化发生在电子显微镜水平上。(3)遗传性视网膜变性小鼠外节段出现中度或明显缩短时，光诱发的IPM变化消失。结果表明，正常外段的存在是IPM光响应发生的必要条件。(4)利用与α 2,6-唾液基转移酶mRNA互补的反义RNA探针原位杂交组织化学方法发现，α 2,6-唾液基转移酶mRNA在大鼠视网膜中的表达在出生后第14天至第16天增加，此时光诱发的IPM变化首次发生。结果表明，糖链末端唾液酸的存在对IPM产生光响应起重要作用。(5)测定了猴视网膜IPM的电阻。周围视网膜的电阻低于黄斑，提示杆状相关IPM的电阻低于锥状相关IPM的电阻。

(1) The light-evoked changes of the interphotoreceptor matrix (IPM) were observed in green- and blue-light-adapted rats, whereas they were not detected in red-light-adapted animals. The results indicate that rod photoreceptors are predominantly responsible for light-evoked changes in the IPM.(2) By electron microscopic examination, the granular components of the IPM were diffusely detected around outer segments in dark-adapted rats, whereas they were observed to be accumulated on the apical process of the retinal pigment epithelia in light-adapted animals. The light-evoked change of the IPM is proved to occur on electron microscopic level.(3) The light-evoked changes of the IPM were observed to be extinct when the outer segments became moderately or markedly shortened in mice with inherited retinal degeneration. The results indicate that the presence of normal outer segments is necessary for the light response of the IPM to occur.(4) By in situ hybridization histochemistry using antisense RNA probes complementary for alpha2,6-sialyltransferase mRNA, its expression in rat retinas was increased between post-natal day (P) 14 and P16, when the light-evoked change in the IPM first occurs. The results indicate that the presence of sialic acid on the termini of sugar chains plays an important role in generating the light responece of the IPM.(5) The electrical resistance of the IPM of the monkey retina was measured. The resistance of the peripheral retina was lower than that of the macula, suggesting that the electrical resistance of the rod associated IPM is lower than that of the cone associated IPM.