Linked Life Data

9077135

Source:http://linkedlifedata.com/resource/pubmed/id/9077135

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1997-4-15
pubmed:abstractText
To determine the role of major chromophores of the human retinal pigment epithelium (RPE) in photooxidation of ascorbate, we monitored spectrophotometrically rates of ascorbate depletion, induced by blue light, in suspensions of human RPE melanin, melanolipofuscin and lipofuscin and in preparation of pigmented and nonpigmented bovine RPE cells. The results clearly show that melanin is the key retinal pigment responsible for the photosensitized oxidation of exogenous ascorbate. To elucidate the mechanism of the photooxidation process, we used purified RPE melanin granules and synthetic dopa (dihydroxyphenylalanine) melanin and employed electron spin resonance (ESR) spectroscopy, ESR oximetry and oxidase electrode. Our data indicate that photoinduced melanin radicals oxidize ascorbate via one-electron transfer reaction. The reduced melanin is reoxidized by molecular oxygen with the formation of superoxide anion and hydrogen peroxide, while the ascorbate radicals decay by disproportionation. Because in the absence of oxygen, no measurable oxidation of ascorbate is observed, it can be concluded that melanin acts as an electron transfer agent. Biological implications of this study remain unclear; however, the formation of oxygen-reactive species that accompany melanin-mediated photooxidation of ascorbate may represent a potential risk to the RPE that should be minimized by yet unknown cellular mechanisms.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0031-8655
pubmed:author
pubmed:issnType
Print
pubmed:volume
65
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
472-9
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
The role of retinal pigment epithelium melanin in photoinduced oxidation of ascorbate.
pubmed:affiliation
Department of Biophysics, Jagiellonian University, Kraków, Poland.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't