McEwen B S, Grafstein B
J Cell Biol. 1968 Sep;38(3):494-508. doi: 10.1083/jcb.38.3.494.
(a) After injection of labeled leucine into the eye of goldfish, radioactive protein rapidly accumulates in the contralateral optic tectum in the layer containing the synaptic endings of the optic fibers. This material reaches the tectum 6-12 hr after the isotope injection, a fact which indicates that the rate of transport is at least 40 mm per day. (b) This rapidly transported material has been shown to consist exclusively of protein, in which the label remains attached to leucine. (c) Inhibition of protein synthesis in the retina prevents the appearance of the transported protein in the tectum, but inhibition of protein synthesis in the tectum does not. Substances having some of the same properties as leucine, such as cycloleucine and norepinephrine, are not transported to the tectum. These experiments all indicate that the transported protein is synthesized in the retina. However, inhibition of retinal protein synthesis after this protein has been formed does not interfere with the transport mechanism itself. (d) The fast component consists of about 85% particulate material. It may be distinguished from a slowly moving component, transported at 0.4 mm per day, which contains about 5 times as much radioactivity as the fast component, and which consists of 60% particulate matter and 40% soluble protein.
(a) 向金鱼眼中注射标记的亮氨酸后，放射性蛋白质迅速在对侧视顶盖中含有视神经纤维突触末梢的层中积累。这种物质在同位素注射后6 - 12小时到达视顶盖，这一事实表明运输速度至少为每天40毫米。(b) 已证明这种快速运输的物质仅由蛋白质组成，其中标记物仍与亮氨酸相连。(c) 视网膜中蛋白质合成的抑制会阻止运输蛋白在视顶盖中出现，但视顶盖中蛋白质合成的抑制则不会。具有与亮氨酸一些相同性质的物质，如环亮氨酸和去甲肾上腺素，不会被运输到视顶盖。这些实验都表明运输蛋白是在视网膜中合成的。然而，在这种蛋白质形成后抑制视网膜蛋白质合成并不会干扰运输机制本身。(d) 快速成分约由85%的颗粒物质组成。它可以与以每天0.4毫米的速度运输的缓慢移动成分区分开来，后者所含放射性约为快速成分的5倍，由60%的颗粒物质和40%的可溶性蛋白质组成。
