May 2007
Volume 48, Issue 13
ARVO Annual Meeting Abstract  |   May 2007
Localisation of Ion Channels Within the Chicken Choroid
Author Affiliations & Notes
  • I. G. Morgan
    ARC Centre of Excellence in Vision Science, Australian National University, Canberra, Australia
  • R. S. Ashby
    ARC Centre of Excellence in Vision Science, Australian National University, Canberra, Australia
  • B. Walcott
    ARC Centre of Excellence in Vision Science, Australian National University, Canberra, Australia
  • P. Megaw
    Department of Physiology and Pharmacology, James Cook University, Canberra, Australia
  • Footnotes
    Commercial Relationships I.G. Morgan, None; R.S. Ashby, None; B. Walcott, None; P. Megaw, None.
  • Footnotes
    Support ARC Centre of Excellence in Vision Science (CEO561903) and the ACT Health and Medical Research Support Program
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 5936. doi:
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      I. G. Morgan, R. S. Ashby, B. Walcott, P. Megaw; Localisation of Ion Channels Within the Chicken Choroid. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5936.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose:: In response to myopic defocus, the choroid expands massively in volume. Tissue swelling of this kind must involve ion and fluid transport, regulated by ion channels such as the sodium, potassium, chloride co-transporter 1 (NKCC1), and the sodium hydrogen exchanger (NHE), and a range of other ion channels. We aimed to localise some of these ion channels using immunohistochemical techniques.

Methods:: Twelve day-old male Australorp chickens were killed with an overdose of carbon dioxide. Eyes were removed and fixed in 4% paraformaldehyde for 4h before being placed in 25% sucrose in PBS for a minimum of 12h. Frozen sections were then cut and stained for NKCC1 and NHE. For histology, eyes were fixed overnight in a 4% formaldehyde solution, before dehydration and resin embedding.

Results:: The choroid is composed of two major compartments - a vascular compartment that borders the retinal pigment epithelium, and a vacuolar/lymphatic compartment which is adjacent to the sclera. Light microscopy demonstrated that most of the expansion took place within the vacuolar/lymphatic compartment, while there was little change in the vascular compartment. Both ion channels were localised to a narrow band of tissue at the border between the two major compartments of the chicken choroid.

Conclusions:: The immunohistochemical localisation of two major ion channels involved in fluid movements, at the border between the vascular and vacuolar/lymphatic compartments of the choroid, suggests that choroidal expansion primarily involves ion and fluid movement from the vascular compartment of the choroid to the vacuolar/lymphatic compartment. The location of NKCC1 and NHE between the two compartments suggests that these transporters may play an important regulatory role in the response of the choroid to myopic defocus. This presumably involves the action of signals which are ultimately of retinal origin, which regulate ion and fluid transport across this boundary.

Keywords: myopia • choroid • ion transporters 

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