Nuclear progestin receptors in rat thymic tissue.
The thymus and its associated endothelial cells and lymphocytes act as an important immunological tissue. The endothelial cells of the thymus have been reported to synthesize cytoplasmic progestin receptor in response to estrogen priming. To measure nuclear progestin receptor, female rats were castrated and primed for 3 days with estradiol benzoate (30 micrograms/0.1 ml/d) and immediately before sacrifice injected subcutaneously with 0.2 mg of progesterone. By Scatchard plot analysis we found that specific progestin receptor (KA = 0.89 +/- 0.10 x 10(9) M-1) was present in the KCl-nuclear extract. The concentration of nuclear progestin receptor was found to be in the range of 312.6 +/- 49 fmole/g tissue (n = 9, 1 hour after progesterone injection) while the nuclear receptor was significantly reduced (approximately 44 fmol/g tissue) in the oil treated controls. This level verges on the limits of sensitivity for this assay. For cytoplasmic progestin receptor the concentration was 3.46 +/- 0.20 pmole/g tissue in oil treated controls (n = 14) and 3.36 +/- 0.20 pmole/g tissue in progesterone treated animals (n = 24). The KA of this thymic cytoplasmic progestin receptor was 1.35 +/- 0.06 x 10(9) M-1. By competition assay, the relative binding affinity of nuclear progestin receptor was: R5020 (a potent synthetic progestin) (100%), progesterone (9%), testosterone (0.56%), corticosterone (0.53%), estradiol-17 beta (0%). It is concluded that thymic reticuloepitheleal cells contain nuclear progestin receptor and this finding supports the hypothesis that progesterone, like other sex steroids may play a regulatory role in thymic cell function.
Fujii-Hanamoto
H
H
Research Service, Veterans Administration Medical Center, Cincinnati, Ohio.
Grossman
C J
CJ
Roselle
G A
GA
Mendenhall
C L
CL
Seiki
K
K
D000818:Animals; D002467:Cell Nucleus / Q000032:analysis*; D003593:Cytoplasm / Q000032:analysis; D005260:Female; D011397:Promegestone / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011980:Receptors, Progesterone / Q000032:analysis*; D013950:Thymus Gland / Q000032:analysis*
D011980:Receptors, Progesterone; D011397:Promegestone