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Related Experiment Videos

Equatorial potassium currents in lenses.

B E Wind1, S Walsh, J W Patterson

  • 1Department of Physiology, University of Connecticut Health Center, Farmington 06032.

Experimental Eye Research
|February 1, 1988
PubMed
Summary

This study reveals that lens currents are primarily potassium-driven at the equator and sodium-driven at the poles. Lens deformation alters these currents by increasing sodium permeability, affecting electrical potential differences.

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Area of Science:

  • Ophthalmology
  • Biophysics
  • Cell Physiology

Background:

  • Previous research identified outward potassium currents at the lens equator and inward sodium currents at the optical poles.
  • The relationship between steady currents (J) and measured potential difference (PD) needed further elucidation.
  • Understanding lens membrane characteristics and ion transport is crucial for visual function.

Purpose of the Study:

  • To quantify lens electrical currents and their relationship to potential differences using microelectrodes.
  • To determine the ionic basis of equatorial currents and investigate the role of ion-specific resistances.
  • To assess the effects of mechanical deformation on lens electrical properties and ion permeabilities.

Main Methods:

  • Utilized vibrating probe and microelectrode techniques to measure steady currents (J) and potential differences (PD) in rat and frog lenses.

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  • Injected outward current (I) to determine membrane resistances and the potential difference at zero net potassium current (PDJ = 0).
  • Applied graded mechanical deformation to the lens and observed reversible changes in electrical parameters.

    • Main Results:

    • Confirmed outward equatorial currents are potassium-driven, with PDJ = 0 values aligning with potassium equilibrium potentials (86 mV in rats, -95 mV in frogs).
    • Demonstrated that injected current alters PD and equatorial current (J), suggesting partially linked electrical loops for K+ and Na+ influenced by the Na, K-pump.
    • Lens deformation reversibly increased equatorial current (J) and decreased negative PD, attributed to increased sodium permeance rather than altered potassium gradients.

    Conclusions:

    • The study provides strong evidence for potassium as the primary charge carrier for outward equatorial lens currents.
    • Lens electrical properties are modulated by mechanical stress, primarily through changes in sodium permeability.
    • These findings enhance our understanding of lens electrophysiology and its response to physical stimuli.