Endothelin receptor A is expressed and mediates the [Ca2+]i mobilization of cells in human ciliary smooth muscle, ciliary nonpigmented epithelium, and trabecular meshwork

Curr Eye Res. 1998 Jan;17(1):31-8. doi: 10.1076/ceyr.


Purpose: To identify which endothelin receptor subtype is expressed and is functional in the human ciliary body and trabecular meshwork, tissues that regulate aqueous humor dynamics.

Methods: Immunocytochemistry was used to characterize the primary culture cells of normal human ocular cells. Endothelin receptor gene expression was probed with reverse transcription of polymerase chain reaction (RT-PCR). Intracellular calcium ([Ca2+]i) mobilization was measured with video image microscopy using Fura-2AM as a fluorescent probe.

Results: Identities of primary cultures, human ciliary smooth muscle (HCSM), ciliary nonpigmented epithelial (HCE), and trabecular meshwork (HTM) cells were confirmed by immunocytochemistry, using cell-specific markers and observing typical cell morphologies. The presence of endothelin receptor A (ETA) was detected with RT-PCR in all three types of cells. The mRNA phenotype was verified with restriction enzyme BamHI digestion. No ETB receptor subtype expression was detected with RT-PCR under the cell culture conditions used. The [Ca2+]i of HCSM cells was increased from 57 +/- 7 nM to 328 +/- 108 nM (n = 23; mean +/- SE; P < 0.05) by 1 nM endothelin-1 (ET-1). In HCE cells, [Ca2+]i increased from 40 +/- 3 nM to 90 +/- 10 nM (n = 55) (P < 0.001) with the same concentration of ET-1. Similarly, ET-1 (1 nM) increased the [Ca2+]i from 51 +/- 6 nM to 185 +/- 47 nM (n = 19) (P < 0.001) in the HTM cells. The agonist for ETB, S6c, had no effect on [Ca2+]i transients in all three cell types. No ETB receptor expression was detected in these cell types under the experimental and culture conditions.

Conclusion: ETA receptor is expressed and is possibly responsible for mediating the signal for [Ca2+]i mobilization by ET-1 in human ciliary smooth muscle, ciliary nonpigmented epithelial cells, and trabecular meshwork cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism*
  • Cell Culture Techniques
  • Ciliary Body / cytology
  • Ciliary Body / drug effects
  • Ciliary Body / metabolism*
  • DNA Primers / chemistry
  • Endothelin-1 / pharmacology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • Fluorescent Antibody Technique, Indirect
  • Fluorescent Dyes / metabolism
  • Fura-2 / metabolism
  • Gene Expression
  • Humans
  • Muscle, Smooth / cytology
  • Muscle, Smooth / drug effects
  • Muscle, Smooth / metabolism*
  • Polymerase Chain Reaction
  • Receptor, Endothelin A
  • Receptors, Endothelin / genetics
  • Receptors, Endothelin / metabolism*
  • Trabecular Meshwork / cytology
  • Trabecular Meshwork / drug effects
  • Trabecular Meshwork / metabolism*
  • Transcription, Genetic


  • DNA Primers
  • Endothelin-1
  • Fluorescent Dyes
  • Receptor, Endothelin A
  • Receptors, Endothelin
  • Calcium
  • Fura-2