Formation of all-trans retinol after visual pigment bleaching in mouse photoreceptors.

Full Abstract

PURPOSE: To test whether the formation of all-trans retinol limits the regeneration of the visual pigment. all-trans retinol is formed after visual pigment bleaching through the reduction of all-trans retinal in a reaction involving NADPH. This reduction begins the recycling of the chromophore for the regeneration of the visual pigment. METHODS: Experiments were performed with dark-adapted, isolated retinas and isolated photoreceptor cells from wild-type and Nrl(-/-) mice. The photoreceptors of Nrl(-/-) mice are conelike and contain only cone pigments. The formation of all-trans retinol after pigment bleaching was measured by quantitative HPLC of retinoids extracted from isolated retinas and by imaging the fluorescence of retinol in photoreceptor outer segments. Experiments were performed at 37 degrees C. RESULTS: In rods, the formation of all-trans retinol proceeded with first-order kinetics, with a rate constant of 0.06 +/- 0.02 minute(-1), significantly faster than the reported rate constant for rhodopsin regeneration. In Nrl(-/-) photoreceptors, the formation of all-trans retinol occurred at least 100 times faster than in rods. For both cell types, the fraction of all-trans retinal converted to all-trans retinol at equilibrium is approximately 0.8, indicating the presence of a similar fraction of reduced NADPH. CONCLUSIONS: Formation of all-trans retinol does not limit the regeneration of bleached visual pigment. Formation of all-trans retinol in the cone-like Nrl(-/-) photoreceptors is much faster than in rods, consistent with a faster regeneration of the visual pigment after bleaching. Different types of photoreceptors contain a comparable fraction of reduced NADPH to drive the reduction of all-trans retinal.

Author information

Author/s: Chen, Chunhe (C); Blakeley, Lorie R (LR); Koutalos, Yiannis (Y);

Affiliation: Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, USA.

Grants: C06 RR015455 (Agency:NCRR NIH HHS) ; EY04939 (Agency:NEI NIH HHS) ; EY14850 (Agency:NEI NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci), published in United States. (Language: eng)

Reference: 2009-Aug; vol 50 (issue 8) : pp 3589-95

Dates: Created 2009/07/29; Completed 2009/08/11; Revised 2009/08/12;

PMID: 19264891, status: MEDLINE (last retrieved date: 8/21/2009)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

External Links for this article
(including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.

MeSH headings (categories)

This article was linked to the MeSH Headings (categories) shown below.

Mice, Inbred C57BL
Mice, Knockout
Microscopy, Fluorescence
NADP - metabolism
Photoreceptor Cells, Vertebrate - metabolism; radiation effects
Retinal Pigments - metabolism
Vitamin A - biosynthesis

Note: Bold headings indicate primary MeSH headings or qualifiers.

Associated Chemicals: Basic-Leucine Zipper Transcription Factors (0) ; Eye Proteins (0) ; Nrl protein, mouse (0) ; Retinal Pigments (0) ; Vitamin A (11103-57-4) ; NADP (53-59-8)

These are the most related articles currently in our database: