Differential Subcellular Localization of Zinc in the Rat RetinaTakumi Akagia, Makoto Kanedab, Katsuyoshi Ishiia, and Tsutomu Hashikawaaa Laboratory for Neural Architecture, Brain Science Institute, RIKEN, Wako, Saitama, Japan b Department of Physiology, Keio University School of Medicine, Tokyo, Japan Correspondence to: Makoto Kaneda, Dept. of Physiology, Keio Univ. School of Medicine, Tokyo 160-8582, Japan. E-mail: mkaneda@physiol.med.keio.ac.jp In the retina, zinc is believed to be a modulator of synaptic transmission and a constituent of metalloenzymes. To determine whether the intracellular localization of zinc correlates with function, we examined the localization of endogenous zinc in the rat retina using the silver amplification method. By light microscopy, reaction products were detected in the pigment epithelial cells (PE), the inner segment of photoreceptors (IS), the outer nuclear layer (ONL) and the inner nuclear layer (INL), the outer plexiform layer (OPL) and the inner plexiform layer (IPL), and the ganglion cell layer (GC). The heaviest accumulation of precipitate was observed in PE and IS, whereas only a little precipitate was found in GC. When the intracellular zinc was chelated with diethyldithiocarbamate, a small amount of precipitate was observed only in ONL. By electron microscopy, zinc was associated with three compartments. In OPL and IPL, zinc was associated with neural processes, while in PE, IS, INL, and GC it was associated with the Golgi apparatus. In ONL, zinc was associated with the nucleus. Zinc in the neural processes is believed to act as a modulator of synaptic transmission, and zinc associated with the Golgi apparatus is assumed to catalyze metalloenzyme reactions. (J Histochem Cytochem 49:8796, 2001) Key Words: synaptic terminal, Golgi apparatus, silver amplification, pigment epithelial cell, electron microscopy
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