1990 Fiscal Year Final Research Report Summary
Research for Brown Pigmentation of Brunescent Cataractous Lenses and For
| Project/Area Number |
01570153
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Pathological medical chemistry
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| Research Institution | Department of Biochemistry, Kanazawa University School of Medicine |
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Principal Investigator |
TOMODA Akiko Department of Biochemistry, Associate Professor, 医学部, 助教授 (10092793)
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| Co-Investigator(Kenkyū-buntansha) |
TAKIZAWA Takenori Department of Biochemistry, Assistant, 医学部, 助手 (40192158)
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| Project Period (FY) |
1989 – 1990
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| Keywords | Brunescent cataracts / Lenses / Pigmentation / Pigmentationーinhibiting substances |
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| Research Abstract |
We analyzed the brown pigments of brunescent lenses obtained from patients with cataracts by using optical methods such as integrating sphere till last year, and deduced that the brown pigments might be xanthommatin or its analogues which were produced by the oxidative dimerizaiton of 3-hydroxykynurenine. As for the mechanism of the formation of brown pigments in brunescent cataractous lenses, we considered that the tryptophan residues of lens proteins were, first of all, converted to 3-hydroxykynurenine residues in the proteins by means of UV irradiation of sun, and then free 3-hydroxykynurenine was added to this 3-hydroxykynurenine residues in the proteins, resulting in the formation in the proteins.
Thus, we investigated whether 3-hydroxykynurenine and its analogues such as 3-hydroxyanthranilic acid and oーaminophenol were additively bound to 3-hydroxykynurenine residues of the lens proteins under irradiation of UV. The experiments were performed at 25^ﾟC for 48 hours. As a result, th
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ese compounds strongly bound to lens proteins, and the color of the lens proteins changed from pale yellow to brown or orange-colored. It was very difficult to isolate these pigmented compounds from the lens proteins. The absorption spectra of these pigmented proteins showed typical ones with peaks at visible and at near-violet regions. These results show that 3-hydroxykynurenine and its analogues bound to 3-hydroxykynurenine residues of the lense proteins by means of UV irradiation. These results also support our prevoius views that 3-hydroxykynurenine combine with 3-hydroxykynurenine residues of the lens proteins to form xanthommatin.
Furthermore, we investigated the pigmentationーinhibiting compounds which may inhibit the brown pigmentation, utilizing the findings that pale yellow lens proteins are pigmented strongly with oーaminophenol under the irradiation of UV for 48 hours. Especially we examined the effects of antioxidants such as ascorbic acid and reduced gluthathione. However, these compounds showed little effects on inhibiting the pigmentation of lens proteins. We are now continuing to find the pigmentationーinhibiting substances using such experimental systems. Less
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