April 2009
Volume 50, Issue 13
ARVO Annual Meeting Abstract  |   April 2009
Is Potassium the Endothelial Derived Hyperpolarizing Factor in Choroid?
Author Affiliations & Notes
  • S. G. Crewther
    Psychological Science, La Trobe University, Melbourne, Australia
  • B. M. Junghans
    Optometry, UNSW, sydney, Australia
  • Footnotes
    Commercial Relationships  S.G. Crewther, None; B.M. Junghans, None.
  • Footnotes
    Support  None.
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 1618. doi:
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      S. G. Crewther, B. M. Junghans; Is Potassium the Endothelial Derived Hyperpolarizing Factor in Choroid?. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1618.

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

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Purpose: : Fluctuations in potassium levels within and around blood vessels have been proposed as a likely controller for the regulation of blood pressure and flow1 throughout the body though this hypothesis has not been explored in the choroidal vasculature. Thus we hypothesized that changes in choroidal abundance of potassium [K], and associated sodium [Na] and chloride [Cl] would parallel thickness and morphological changes as measured with transmission electronmicroscopy in the chick model of induction and recovery from form deprivation.

Methods: : Hatchling chickens were raised with monocular translucent occluders from day 3 -14. After occluder removal, chicks were given variable hours (T=0-120hrs) of visual experience then eyes were enucleated and retina/RPE/choroidal tissue prepared for light and electron microscopy and elemental microanalysis.

Results: : At occluder removal, significant increases in K, Na and Cl ion abundance were seen in the extravascular space of the choroid but not within the lymphatic sinusoids. Within 24 hours of occluder removal choroidal thickness and choroidal [K] return to normal range as previously reported for choroidal blood flow2. By comparison choroidal Na and Cl levels remain high until refractive normalization (~T=120hrs) even though choroidal thickness had still not returned to control levels. Ultrastructurally, occlusion led to a drastic reduction in the number of fenestrations on the retinal side of the choriocapillaris vessels and also in the lymphatic sinusoids of the outer choroid. By 48 hours post occlusion, the number of fenestrations was back to normal though maximum expansion of choroidal thickness only occurred after 72 hours. Interestingly, up to T=48hrs, as extravascular and choriocapillaris [Na] and [Cl] fell, the concentrations within the lymphatics increased.

Keywords: choroid • ion channels • myopia 

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