Retinoids bound to interstitial retinol-binding protein during light and dark-adaptation.
High-performance liquid chromatography was used to determine the types and amounts of retinoids bound to interstitial retinol-binding protein (IRBP) during light- and dark-adaptation in frogs. IRBP was separated from CRBP and CRA1BP by ion-exchange chromatography and quantitated by determining the amount of Serva Blue R dye bound to it in stained sodium dodecyl sulfate polyacrylamide gels. The amount of IRBP was not significantly different in light- and dark-adapted eyes (0.15 +/- 0.05 nmol/eye compared with 0.18 +/- 0.08 nmol/eye). In the dark-adapted state, IRBP bound mainly 11-cis retinol and 11-cis retinal in quantities that summed to about 1 mol/mol IRBP. After the onset of light-adaptation, all-trans retinol increased from its very low dark-adapted level, peaked at 0.2 mol/mol IRBP and then declined to the dark-adapted level again. Concomitantly, the total retinoid bound to IRBP fell, mainly because there was a drop in the amount of 11-cis retinal. During dark-adaptation, the amount of 11-cis retinal increased. No significant changes were seen in the amount of 11-cis retinol in light and darkness. These findings support the hypothesis that when rhodopsin is bleached IRBP transports all-trans retinol from the retina to the pigment epithelium and that it delivers 11-cis retinal to the rod outer segments for rhodopsin regeneration.
Lin
Z S
ZS
State University of New York, Stony Brook 12246.
Fong
S L
SL
Bridges
C D
CD
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003623:Dark Adaptation; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins; D015151:Immunoblotting; D008027:Light; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D011894:Rana pipiens; D012172:Retinaldehyde / Q000378:metabolism; D012176:Retinoids / Q000378:metabolism*; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D054840:Retinol-Binding Proteins, Cellular; D012243:Rhodopsin / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000378:metabolism; D014801:Vitamin A / Q000378:metabolism; D000099214:Retinol-Binding Proteins, Interstitial
D002352:Carrier Proteins; D005136:Eye Proteins; D012172:Retinaldehyde; D012176:Retinoids; D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; D012243:Rhodopsin; D014801:Vitamin A; D000099214:Retinol-Binding Proteins, Interstitial