In vivo isomerization of all-trans- to 11-cis-retinoids in the eye occurs at the alcohol oxidation state

Journal Article · Tue Oct 21 04:00:00 EDT 1986 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00369a020· OSTI ID:7035567

Bernstein, P S; Rando, R R

The vertebrate biochemical pathway for regeneration of visual pigments in the living eye after bleaching is largely uncharacterized. Since isomerization of an all-trans-retinoid to an 11-cis-retinoid could conceivably occur via the aldehyde, alcohol, or ester forms of vitamin A, it is important to determine the oxidation state of the retinoid that is isomerized in vivo. To address this problem, light-adapted rats and frogs were injected intraperitoneally with a mixture of (15-/sup 3/H)-all-trans-retinol and (15-/sup 14/C)-all-trans-retinol. After 4 or 24 h of dark adaptation, labeled retinoids in the animal's eyes were analyzed. All rats had the expected 50% loss of /sup 3/H label (relative to /sup 14/C) in 11-cis-retinal, a loss of /sup 3/H that must occur when (15-/sup 3/H)retinol is oxidized to retinal. 11-cis-Retinyl esters in the rats' eyes at 4 h retained 67% of the /sup 3/H label, and this could be increased to 81% when the rats were pretreated with 4-methylpyrazole, an alcohol dehydrogenase inhibitor known to inhibit dark adaptation. This result demonstrates that retinoid isomerization occurs at the alcohol oxidation state in the rat eye. Had it occurred at the aldehyde oxidation state, at least 50% of the /sup 3/H in the 11-cis-retinyl esters would have been lost. The importance of this isomerization pathway is emphasized by the observation that dark-adapting rats whose alcohol dehydrogenase(s) had been inhibited by 4-methylpyrazole had increased amounts of 11-cis-retinyl ester in their eyes relative to control rat eyes, a result that is understandable only if retinoids are isomerized in vivo at the alcohol oxidation state.

• Research Organization: Harvard Medical School, Boston, MA
• OSTI ID: 7035567
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 21; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMPHIBIANS
ANIMAL TISSUES
ANIMALS
AQUATIC ORGANISMS
BIOLOGICAL PATHWAYS
BODY
BODY AREAS
CARBON 14 COMPOUNDS
CARBOXYLIC ACID ESTERS
CHEMICAL REACTIONS
EPITHELIUM
ESTERS
EYES
FACE
FROGS
HEAD
IN VIVO
ISOMERIZATION
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
ORGANIC COMPOUNDS
ORGANS
RATS
REDOX REACTIONS
RETINA
RETINOIC ACID
RODENTS
SENSE ORGANS
TISSUES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES
VITAMIN A
VITAMINS