Apoptosis of photoreceptor cells in ornithine-induced retinopathy

Graefes Arch Clin Exp Ophthalmol. 1998 Mar;236(3):207-12. doi: 10.1007/s004170050066.


Background: The intravitreal injection of ornithine produces selective damage to the retinal pigment epithelium (RPE) and results in a loss of RPE, choriocapillaris and photoreceptor cells. To elucidate the mechanism of secondary retinal atrophy, we investigated the presence of apoptotic cells in a rat model of ornithine-induced retinopathy.

Methods: At 6 and 12 h and 1, 2, 4, 7, 14 and 28 days after an intravitreal injection of L-ornithine hydrochloride in rat eyes, we removed the eyes and subjected them to histopathological examination. We detected apoptotic cells by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate digoxigenin nick end labeling (TUNEL) assay, which stains the 3'-OH ends of fragmented DNA. We used electron microscopy to detect the apoptotic cells morphologically.

Results: RPE cells were selectively damaged immediately after ornithine administration. TUNEL-positive photoreceptor cells appeared exclusively in the photoreceptor cell layer 12 h after ornithine administration. The number of TUNEL-positive cells increased throughout the 2 days following the injection, then decreased markedly. TUNEL-positive cells remained until 28 days, when the photoreceptor cells had disappeared. The ganglion cell layer, inner nuclear layer and damaged RPE cells were negative for TUNEL staining during all stages. The electron microscopic study also revealed the pyknotic nuclei of apoptotic photoreceptor cells.

Conclusion: An intravitreal injection of ornithine caused primary damage to the RPE, and subsequently some of the photoreceptor cells revealed apoptosis by TUNEL assay. These findings suggest the dysfunction of the RPE causes photoreceptor cell death according to the intrinsic program of an apoptotic mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis* / drug effects
  • Atrophy
  • DNA Damage
  • DNA Fragmentation
  • DNA Nucleotidyltransferases
  • Deoxyuracil Nucleotides
  • Ornithine / toxicity*
  • Photoreceptor Cells / drug effects
  • Photoreceptor Cells / pathology*
  • Pigment Epithelium of Eye / drug effects*
  • Pigment Epithelium of Eye / pathology
  • Pigment Epithelium of Eye / ultrastructure
  • Rats
  • Rats, Inbred BN
  • Retinal Diseases / chemically induced
  • Retinal Diseases / pathology*


  • Deoxyuracil Nucleotides
  • deoxyuridine triphosphate
  • Ornithine
  • DNA Nucleotidyltransferases