Retinoid processing in retinal pigment epithelium of toad (Bufo marinus)

J Biol Chem. 1994 Sep 2;269(35):21983-9.

Abstract

The formation of 11-cis-[3H]retinal in the retinal pigment epithelium (RPE) and its release to extracellular medium containing interphotoreceptor retinoid-binding protein (IRBP) were studied in the RPE eyecup of the toad (Bufo marinus). The RPE was labeled with all-trans-[3H]retinol during an initial 1-h incubation. In phase 2 of the incubation (0-2 h), the extracellular medium contained initially ligand-free IRBP (0-26 microM). Retinoids subsequently extracted from the extracellular medium and RPE were analyzed by high performance liquid chromatography and scintillation counting. IRBP increased both the molar amount and specific radioactivity of 11-cis-retinal released by the RPE during phase 2. The molar amount of 11-cis-retinal in the RPE was small relative to that of retinal released with high IRBP. With 21 microM IRBP and phase 2 incubations of > or = 10 min, the specific radioactivity of released 11-cis-retinal exceeded that of all-trans-retinyl ester in the RPE. The specific radioactivity of 11-cis-retinyl ester was less than that of all-trans-ester, independent of IRBP concentration. The results indicate that IRBP promotes the formation (from all-trans-precursor) as well as the release of 11-cis-retinal and suggest the preferred utilization of recently incorporated and esterified all-trans-retinol in 11-cis-retinal synthesis in a "last in/first out" manner.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bufo marinus
  • Chromatography, High Pressure Liquid
  • Pigment Epithelium of Eye / metabolism*
  • Retinaldehyde / isolation & purification
  • Retinaldehyde / metabolism
  • Retinoids / metabolism*
  • Retinol-Binding Proteins / metabolism*
  • Scintillation Counting

Substances

  • Retinoids
  • Retinol-Binding Proteins
  • Retinaldehyde