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Nuclear progestin receptors in rat thymic tissue.
H Fujii-Hanamoto1, C J Grossman, G A Roselle
1Research Service, Veterans Administration Medical Center, Cincinnati, Ohio.
Thymus
|February 1, 1990
Summary
The thymus contains nuclear progestin receptors in reticuloepithelial cells, suggesting progesterone influences thymic function. This study quantifies these receptors in female rats after hormone treatment.
Area of Science:
- Endocrinology
- Immunology
- Cell Biology
Background:
- The thymus is a key immunological organ.
- Thymic endothelial cells may synthesize cytoplasmic progestin receptors after estrogen priming.
- The presence and role of nuclear progestin receptors in the thymus are not well understood.
Purpose of the Study:
- To investigate the presence and characteristics of nuclear progestin receptors in the thymus.
- To determine if progesterone, a sex steroid, plays a regulatory role in thymic cell function.
Main Methods:
- Female rats were ovariectomized and treated with estradiol benzoate and progesterone.
- Nuclear and cytoplasmic extracts were prepared from thymic tissue.
- Scatchard plot analysis and competition assays were used to characterize progestin receptors.
Main Results:
- Specific nuclear progestin receptors were detected in thymic KCl-nuclear extracts with a dissociation constant (KA) of 0.89 x 10(9) M-1.
- Nuclear progestin receptor concentration was significantly higher in progesterone-treated rats (312.6 fmole/g tissue) compared to controls (44 fmole/g tissue).
- Cytoplasmic progestin receptors were present in similar concentrations in both treated and control groups, with a KA of 1.35 x 10(9) M-1.
Conclusions:
- Thymic reticuloepithelial cells possess nuclear progestin receptors.
- These findings support the hypothesis that progesterone, similar to other sex steroids, may regulate thymic cell function.