Document Detail


L-DOPA produced nitric oxide in the vitreous and caused greater vasodilation in the choroid and the ciliary body of melanotic rats than in those of amelanotic rats.
MedLine Citation:
PMID:  11549108     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The nitrogen cycle initiates direct reduction of N2 to NH3 by enzymatic reactions. We hypothesize that L-dihydroxyphenylalanine (L-DOPA), a catecholamine, could be a source of nitric oxide (NO). In order to determine whether L-DOPA generates NO and induces any biological change in the eye, we measured the generation of NO in vitro and in vivo, and investigated the histopathological changes caused by injection of L-DOPA into the vitreous of rats. We also hypothesized that melanin granules may affect the generation of NO during the metabolism of L-DOPA, since L-DOPA is a precursor of melanin in the brain and the eye. Therefore, we compared the effects of L-DOPA on the generation of NO between amelanotic and melanotic rats. NO was measured as diffusion currents by NO electrodes. In vitro, various concentrations of L-DOPA (5, 29.9, 79.4, 152.7, and 249 microM) were added to the medium. The inhibition of NO generation by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide (carboxy-PTIO) was tested. In vivo, NO generation in the vitreous of rats was measured and the eyes were enucleated under anesthesia after L-DOPA injection. The ocular tissues were subjected to histological examination. NO was produced from L-DOPA in a dose-dependent manner and was scavenged by carboxy-PTIO in vitro. NO in the vitreous of melanotic rats was generated from L-DOPA. Histological examination with hematoxylin-eosin staining revealed vasodilation in the ciliary vessels and the choroid after L-DOPA injection. Both effects were greater in melanotic rats than in amelanotic rats. The vasodilation may be attributable to NO as well as to superoxides, which can be regulated by the existence of melanin.
Authors:
S K Amaki; Y Oguchi; T Ogata; T Suzuki; K Akeo; T Hiramitsu
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Publication Detail:
Type:  Comparative Study; In Vitro; Journal Article    
Journal Detail:
Title:  Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society     Volume:  14     ISSN:  0893-5785     ISO Abbreviation:  Pigment Cell Res.     Publication Date:  2001 Aug 
Date Detail:
Created Date:  2001-09-10     Completed Date:  2002-02-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8800247     Medline TA:  Pigment Cell Res     Country:  Denmark    
Other Details:
Languages:  eng     Pagination:  256-63     Citation Subset:  IM    
Affiliation:
Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan. satchie@da.so-net.ne.jp
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MeSH Terms
Descriptor/Qualifier:
Animals
Choroid / blood supply
Ciliary Body / blood supply
Dopamine Agents / pharmacology*
Electrodes
Levodopa / pharmacology*
Melanins / physiology
Nitric Oxide / biosynthesis*
Pigmentation / physiology
Rats
Rats, Wistar
Species Specificity
Superoxides / metabolism
Vasodilation / drug effects*
Vitreous Body / metabolism*
Chemical
Reg. No./Substance:
0/Dopamine Agents; 0/Levodopa; 0/Melanins; 10102-43-9/Nitric Oxide; 11062-77-4/Superoxides

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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