title: Selective inner retinal dysfunction in growth hormone transgenic mice.
abstract: OBJECTIVE
  The discovery of locally produced growth hormone (GH) and its receptor in the retina of rodents raises the possibility that GH might modulate retinal function. To test this hypothesis, we determined the retinal electroretinogram (ERG) of bovine GH (bGH) transgenic mice.
  
  
  METHODS
  ERGs were recorded from 11 wild type (WT) and 9 bGH mice, at 2 months of age in response to a series of light flashes at increasing intensity. Three ERG components were assessed for their amplitude and timing: a-wave, b-wave and oscillatory potentials (OPs). OPs were isolated with a 75-300 Hz digital filter. Retina layer sizes, nuclei number and vascularization were assessed by respectively staining cross sections with DAPI and Bandeiraea simplicifolia.
  
  
  RESULTS
  OPs were selectively affected in the bGH mouse compared to WT. When OP amplitude values were normalized to the a-wave amplitude (to account for inter-animal variability in WT and bGH groups), OP2, OP3, and OP4 showed amplitude reductions (of 65%, 72%, and 68%, respectively) in the bGH mouse compared to the WT. This was accompanied by a prolongation of the implicit time for the peak of OP3 (28.1 vs 31.1 ms, WT vs bGH) and OP4 (37.8 vs 41.6 ms), while the implicit time of a- and b-waves were unaffected. Fast Fourier transform analysis revealed that the OPs' dominant frequency was significantly reduced (P<0.05) in the bGH mice (100 Hz) compared to WT (108Hz). There was no significant change in retinal histology except for a significant increase in the axial length of the eye in bGH mice.
  
  
  CONCLUSIONS
  Mice expressing bGH display a selective inner retinal defect as demonstrated using ERG recordings. The specific OP defect observed in these mice is similar to the ERG results obtained in patients with diabetic retinopathy and in related animal models.
authors.affiliation: Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7.
authors.forename: Brent T
authors.initials: BT
authors.lastname: Martin
authors.forename: Edward O
authors.initials: EO
authors.lastname: List
authors.forename: John J
authors.initials: JJ
authors.lastname: Kopchick
authors.forename: Yves
authors.initials: Y
authors.lastname: Sauvé
authors.forename: Steve
authors.initials: S
authors.lastname: Harvey
mesh_terms: D000818:Animals; D002417:Cattle; D004596:Electroretinography; D005260:Female; D013006:Growth Hormone / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010641:Phenotype; D012160:Retina / Q000503:physiopathology*; D012164:Retinal Diseases / Q000175:diagnosis*
chemical_list: C073294:growth hormone, bovine; D013006:Growth Hormone