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Related Experiment Videos

EGTA modulates equatorial currents in frog lenses.

S Walsh1, J W Patterson

  • 1University of Connecticut Health Center, Farmington 06032.

Experimental Eye Research
|November 1, 1989
PubMed
Summary

Removing calcium from frog lenses alters potassium currents (J). The vibrating probe revealed unexpected changes in resistance and voltage, influenced by EGTA and sodium ion concentrations, suggesting a proposed mechanism.

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Area of Science:

  • Ophthalmology
  • Physiology
  • Biophysics

Background:

  • The equatorial potassium current (J) in frog lenses is crucial for lens function.
  • Understanding ion transport mechanisms is vital for maintaining lens transparency and refractive properties.

Purpose of the Study:

  • To investigate the effects of calcium (Ca2+) removal on the equatorial K+ current (J) in frog lenses.
  • To explore the role of EGTA and sodium (Na+) in modulating these currents using a vibrating probe.

Main Methods:

  • Utilized a vibrating probe combined with microelectrodes to measure K+ current (J) in frog lenses.
  • Manipulated bathing medium by removing Ca2+, adding EGTA, and varying Na+ concentrations.
  • Analyzed changes in reversal potential (PDJ = 0), input resistance (R), and segment resistance (RJ).

Main Results:

  • Ca2+ removal without EGTA increased J fourfold, decreased R and RJ, and maintained reversal potential near Nernst potential.
  • Ca2+ removal with EGTA resulted in a twofold J increase, linear current-voltage relationship, and altered PD and reversal potential.
  • Na+ removal and EGTA addition decreased RJ and increased J, showing inverse variation with Na+ concentration; changes were reversible.

Conclusions:

  • Calcium ions play a significant role in regulating K+ current (J) in frog lenses.
  • EGTA and Na+ interact with Ca2+-dependent mechanisms, affecting lens electrical properties.
  • A novel mechanism accounting for these observed changes in ion transport is proposed.

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