title: Postnatal Chick Choroids Exhibit Increased Retinaldehyde Dehydrogenase Activity During Recovery From Form Deprivation Induced Myopia.
abstract: OBJECTIVE
  Increases in retinaldehyde dehydrogenase 2 (RALDH2) transcript in the chick choroid suggest that RALDH2 may be responsible for increases observed in all-trans-retinoic acid (atRA) synthesis during recovery from myopic defocus. The purpose of the present study was to examine RALDH2 protein expression, RALDH activity, and distribution of RALDH2 cells in control and recovering chick ocular tissues.
  
  
  METHODS
  Myopia was induced in White Leghorn chicks for 10 days, followed by up to 15 days of unrestricted vision (recovery). Expression of RALDH isoforms in chick ocular tissues was evaluated by Western blot. Catalytic activity of RALDH was measured in choroidal cytosol fractions using an in vitro atRA synthesis assay together with HPLC quantification of synthesized atRA. Distribution of RALDH2 cells throughout the choroid was evaluated by immunohistochemistry.
  
  
  RESULTS
  RALDH2 was expressed predominately in the chick choroid (P < 0.001) and increased after 24 hours and 4 days of recovery (76%, 74%, and 165%, respectively; P < 0.05). Activity of RALDH was detected solely in the choroid and was elevated at 3 and 7 days of recovery compared to controls (70% and 48%, respectively; P < 0.05). The number of RALDH2 immunopositive cells in recovering choroids was increased at 24 hours and 4 to 15 days of recovery (P < 0.05) and were concentrated toward the RPE side compared to controls.
  
  
  CONCLUSIONS
  The results of this study suggest that RALDH2 is the major RALDH isoform in the chick choroid and is responsible for the increased RALDH activity seen during recovery.
authors.affiliation: Department of Cell Biology University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.
authors.forename: Angelica R
authors.initials: AR
authors.lastname: Harper
authors.affiliation: Department of Cell Biology University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.
authors.forename: Xiang
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.
authors.forename: Gennadiy
authors.initials: G
authors.lastname: Moiseyev
authors.affiliation: Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.
authors.forename: Jian-Xing
authors.initials: JX
authors.lastname: Ma
authors.affiliation: Department of Cell Biology University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.
authors.forename: Jody A
authors.initials: JA
authors.lastname: Summers