KMID : 0360220070480070969
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Journal of the Korean Ophthalmological Society 2007 Volume.48 No. 7 p.969 ~ p.979
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Effects of Zinc and Hypothermic Process during the Light and Dark Adaptation of Vertebrate Retina
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Park Jong-Seok
Kim Hyun-Jung Jung Hyuk Kim Sang-Gi Choi Gui-Hyang Kim Bo-Ae Suh Tae-Soo Kim Sang-Kook Kim You-Young Kim Si-Yeol
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Abstract
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Purpose: The purpose of this study was to clarify the effects of zinc treatment and hypothermia on visual adaptation and visual sensitivity in bullfrogs (Rana catesbeiana), which are poikilothermal animals capable of adjusting quickly to environmental temperature changes.
Methods: The effects of both zinc treatment and hypothermia on visual sensitivity were studied by using electroretinogram (ERG) recording and absorption spectra scanning before and after zinc and TSQ (N-[6-methoxy-8-quinolyl]-p-toluene sulfonamide) treatment, with or without temperature changes.
Results: In spite of malnutrition due to hibernation, the optimal zinc concentration effect was obtained at 10-4M (10-2 M 200 §¡ ZnCl2 in 20 §¢ Ringer¡¯s solution) according to ERG recording. After zinc treatment and hypothermia induction, increments of all ERG components and thresholds were taken by ERG recording. These results showed that both zinc treatment and hypothermia may increase visual sensitivity during visual adaptation. In spectral scans, the absorbance increment due to zinc treatment and hypothermia was shown over the whole spectral range (400~750 nm), and it was especially prominent at ¥á-peak (about 500 nm). In addition, there was a decrease in absorption differences between dark adaptation and light adaptation after zinc treatment. Furthermore, according to the visual sensitivity decrement using TSQ as a zinc specific chelator, this visual sensitivity increase was shown to be caused by zinc.
Conclusions: As the results suggest, both zinc treatment and hypothermic effects may improve visual sensitivity by promoting rhodopsin regeneration and inhibiting rhodopsin bleaching induced by light illumination. Zinc may activate the enzyme activity of retinol dehydrogenase and phosphodiesterase, while hypothermic effects may improve precursor transport, which is required for rhodopsin regeneration, by tightening membrane adhesion between retinas and retinal pigment epithelia. In addition, we believe that zinc treatment and hypothermic effects may work synergistically to accelerate visual sensitivity during visual adaptation.
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KEYWORD
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Absorption Spectra Scanning, Hypothermic Effect, Electroretinogram, ERG, TSQ (N-[6-methoxy-8-quinolyl]-p-toluene sulfonamide), Zinc
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