Nuclear thyroid hormone receptor in the rat uterus

Area of Science:

• Endocrinology
• Molecular Biology
• Reproductive Biology

Background:

• The uterus is a potential target organ for thyroid hormone (T3) action.
• Nuclear receptors for T3 (T3R) mediate the effects of thyroid hormones in target tissues.

Purpose of the Study:

• To determine if rat uterine nuclei contain T3 receptors (T3R).
• To characterize the properties of uterine nuclear T3R and compare them to liver T3R.

Main Methods:

• Established methods to measure T3R concentrations in rat uterine nuclei.
• Prepared nuclear fractions from rat uterus and liver.
• Analyzed specific [125I]T3 binding using Scatchard plots and sucrose density gradients.
• Assessed binding specificity through competition assays with various thyroid hormone analogs.

Main Results:

• Detected a high-affinity binding component for [125I]T3 in both uterine and liver nuclear extracts (Ka = 1.0-3.0 X 10(9) M-1).
• The principal [125I]T3-binding component exhibited a sedimentation coefficient of 3.5-4.0 S in both tissues.
• Demonstrated distinct relative binding affinities for T3 and its analogs in uterine nuclei compared to serum.
• Quantified T3R concentrations: liver (595 +/- 162), kidney (492 +/- 120), uterus (249 +/- 66), and spleen (48 +/- 10) fmol/mg DNA.

Conclusions:

• Provided evidence for the presence of T3R in the nuclear fraction of the rat uterus.
• Uterine nuclear T3R exhibit properties similar to those of liver nuclear T3R.
• These findings support the uterus as a potential target organ for thyroid hormone action.