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/lp/bioscientifica/characterization-and-assay-of-the-progesterone-receptor-in-rat-uterine-miCVFTJIE9
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- Publisher
- Bioscientifica
- Copyright
- Copyright © 1978 The Authors. All Rights Reserved.
- ISSN
- 0022-0795
- eISSN
- 1479-6805
- DOI
- 10.1677/joe.0.0760021
- Publisher site
- See Article on Publisher Site
Abstract
SUMMARYThe synthetic progestogen R5020 (17,21-dimethyl-19-norpregna-4,9-diene-3,20-dione) binds with high affinity (Ka = 8·8 × 108 1/mol at 0 °C) to the progesterone receptor from rat uterine cytosol. At nanomolar concentrations, equilibrium is attained in less than 90 min. R5020 has a very low affinity for other specific steroid-binding proteins (corticosteroid-binding globulin and oestrogen receptors) present in relatively high concentrations in the uterine cytosol. The affinity of the receptor for the natural hormone progesterone is remarkably low (Ka= 1 × 108−1·7 × 1081/mol at 0 °C) which explains the instability of progesterone–receptor complexes. Advantage may be taken of this property to remove endogenous progesterone easily by charcoal treatment at 0 °C, a treatment which does not modify the concentration of receptors. A method based on these characteristics is described for the assay of the total number (progesterone-bound and unbound) of receptor sites in uterine cytosol. This assay may be used in various physiological situations where endogenous progesterone is present at unknown concentrations.
Journal
Journal of Endocrinology – Bioscientifica
Published: Jan 1, 1978