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Tamoxifen blocks chloride channels. A possible mechanism for cataract formation

J J Zhang1, T J Jacob, M A Valverde

  • 1Department of Physiology, University of Wales, Cardiff, United Kingdom.

The Journal of Clinical Investigation
|October 1, 1994
PubMed

Insights

Tamoxifen, used for breast cancer, blocks eye chloride channels, potentially causing cataracts. This finding reveals a new cellular target for tamoxifen beyond estrogen receptors.

Area of Science:

  • Pharmacology
  • Ophthalmology
  • Molecular Biology

Background:

  • Tamoxifen is a widely used antiestrogen for breast cancer treatment and prevention.
  • Clinical use of tamoxifen is associated with visual side effects, including cataract formation.

Purpose of the Study:

  • To investigate the molecular mechanism underlying tamoxifen-induced cataracts.
  • To identify alternative cellular targets of tamoxifen.

Main Methods:

  • Investigated tamoxifen's interaction with specific chloride channels.
  • Utilized organ culture of eye lenses to assess tamoxifen's effect on lens opacity.
  • Examined tamoxifen's blockade of chloride channels independently of estrogen receptor interaction.

Main Results:

  • Tamoxifen and its derivatives act as high-affinity blockers of specific chloride channels.
  • Chloride channel blockade by tamoxifen was independent of estrogen receptor binding.
  • Tamoxifen induced lens opacity and cataract formation in organ culture at clinically relevant concentrations.

Conclusions:

  • Tamoxifen's blockade of ocular chloride channels provides a molecular explanation for cataract formation.
  • These findings highlight a novel cellular target for tamoxifen, distinct from its antiestrogen activity.
  • The results have implications for the clinical use of tamoxifen and related antiestrogens, particularly regarding visual side effects.

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