Synthesis of retinoids by human retinal epithelium and transfer to rod outer segments.
The synthesis and release of 11-cis-retinoids by primary cultures of human retinal pigment epithelium (RPE) and the transfer of these retinoids to co-incubated human rod outer segments (ROS) were studied. Monolayers of 2-3-week-old cultured RPE incorporate tritiated all-trans-retinol, esterify it to the corresponding retinyl palmitate, form 11-cis-retinol and 11-cis-retinaldehyde and release retinaldehyde into the culture medium. The ratio of 11-cis to all-trans isomers of retinol, retinyl palmitate and retinaldehyde formed in the cells along with retinaldehyde released and incorporated into the ROS progressively increases, indicating a progressive increase in the concentration of 11-cis isomer from the time it is formed in RPE cells until its transfer to ROS. Incorporation of 11-cis-retinaldehyde into the ROS is directly related to the amount of albumin present in the media, suggesting the transfer of retinoids from RPE to photoreceptor to be a protein-mediated process. Events leading to isomerization, esterification, oxidation and release of retinoids by human RPE and incorporation of retinoids into ROS can therefore be examined in vitro.
Das
S R
SR
Department of Ophthalmology, Columbia University, New York, NY 10032.
Bhardwaj
N
N
Gouras
P
P
D000328:Adult; D000368:Aged; D001692:Biological Transport; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004224:Diterpenes; D004951:Esterification; D006801:Humans; D007700:Kinetics; D008875:Middle Aged; D010084:Oxidation-Reduction; D010786:Photoreceptor Cells / Q000378:metabolism*; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D012172:Retinaldehyde / Q000378:metabolism; D012176:Retinoids / Q000378:metabolism*; D000084562:Retinyl Esters; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D013237:Stereoisomerism; D014801:Vitamin A / Q000031:analogs & derivatives / Q000378:metabolism
D004224:Diterpenes; D012176:Retinoids; D000084562:Retinyl Esters; D014801:Vitamin A; C014794:retinol palmitate; D012172:Retinaldehyde