Histochemical localization of zinc and copper in rat ocular tissues

Zinc and copper were histochemically localized in rat ocular tissues. Zinc was demonstrated by the dithizone method, and copper by the rubeanic acid and rhodanine methods. The retinal photoreceptor's outer segment showed the presence of zinc, but no zinc reaction was seen in other parts of the retina or other ocular tissues, even in rats fed excess zinc. It seems that photoreceptor cells contain the highest concentration of zinc. Copper was seen in the corneal epithelium and endothelium, iris, ciliary body, lens epithelium, retinal outer nuclear layer, photoreceptor inner and outer segments, retinal pigment epithelium, choroid, sclera, and optic nerve. These trace elements seems to play roles as components of some metalloenzymes and may have other functions till now unknown.