Down-regulation of the mdr gene by thyroid hormone during Xenopus laevis development

Shoshanna N. Zucker, Gonzalo Castillo, Susan Band Horwitz

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The developmental regulation of mdr in Xenopus laevis has been investigated. Xe-mdr expression was first detected in the early tadpole stage just prior to the onset of feeding and increased during intestinal development, with a sharp decline at metamorphosis. Xe-mdr expression was found to be localized specifically to the epithelial cells lining the intestinal tract. When premetamorphic tadpoles were treated with 5 nM triiodothyronine to induce metamorphosis, a significant decrease in mdr message and protein was observed after 3 days, a time at which the primary epithelium remained intact. Furthermore, in thyroid-hormone treated primary cultures of brush border epithelial cells, a reduction in mdr message also was observed. These results demonstrate that the Xe-mdr gene is developmentally regulated and suggest a role for thyroid hormone in this process. This is the first report of a naturally occurring substance that can down-regulate mdr gene expression in vivo.

Original languageEnglish (US)
Pages (from-to)73-81
Number of pages9
JournalMolecular and Cellular Endocrinology
Issue number1
StatePublished - Apr 25 1997


  • Metamorphosis
  • Multidrug resistance
  • P-glycoprotein
  • Triiodothyronine
  • Xenopus laevis

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Endocrinology


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