Localization of endothelin-1 mRNA expression and immunoreactivity in the anterior segment of human eye: expression of ETA and ETB receptors

Mol Vis. 2003 Apr 9:9:103-9.


Purpose: Endothelin-1 (ET-1), a potent vasoactive peptide, is an important regulator of intraocular pressure. Actually, there is evidence of a role for ET-1 in the pathogenesis of glaucoma. However, the expression pattern of ET-1 and its receptors, ETA and ETB, in the anterior segment of human eye are not known. In the current study, we have examined the expression and distribution of ET-1 as well as the expression profile of ETA and ETB genes in the iris, ciliary muscle, and ciliary processes of human eyes.

Methods: Six normal human eyes with no history of eye diseases were fixed, embedded in paraffin and sectioned. Cellular localization of ET-1 was identified by in situ hybridization and immunohistochemistry. Iris, ciliary processes, and ciliary muscles were dissected from six normal human eyes and quantitative real time RT-PCR was used to quantify the expression of ETA and ETB.

Results: In situ hybridization revealed the presence of ET-1 transcripts in the iris, nonpigmented epithelial ciliary cells, and ciliary muscle. Immunohistochemical studies showed that ET-1-like immunoreactivity appeared in the same regions where ET-1 mRNA was expressed as well as in trabecular cells, inner and outer endothelial cells lining Schlemm's canal, corneal epithelial, and limbus cells. Quantitative real time RT-PCR demonstrated that the expression of ETA and ETB receptors is greatest in the iris, followed by ciliary muscle and ciliary processes.

Conclusions: ET-1 and its receptors ETA and ETB are constitutively expressed in the anterior segment of human eye. These results indicate that ET-1 may play a physiological role in the regulation of intraocular pressure through its ETA and ETB receptors in human eye. In addition, ET-1 present in corneal epithelium and limbus may function in regulating cell proliferation and/or differentiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Anterior Eye Segment / metabolism*
  • Ciliary Body / metabolism
  • Endothelin-1 / genetics*
  • Endothelin-1 / metabolism
  • Female
  • Gene Expression*
  • Humans
  • Immunoenzyme Techniques
  • In Situ Hybridization
  • Iris / metabolism
  • Male
  • Muscle, Smooth / metabolism
  • RNA, Messenger / metabolism*
  • Receptor, Endothelin A
  • Receptor, Endothelin B
  • Receptors, Endothelin / genetics*
  • Receptors, Endothelin / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction


  • Endothelin-1
  • RNA, Messenger
  • Receptor, Endothelin A
  • Receptor, Endothelin B
  • Receptors, Endothelin