Binding of progesterone by rat myometrium during pregnancy and by human myometrium in late pregnancy |
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| Authors: | M Haukkamaa |
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| Affiliation: | 1. University of Texas Health Science Center at San Antonio, Departments of Neurosurgery and Neurology, 7703 Floyd Curl Drive, MC# 7843, San Antonio, TX 78299-3900, United States;2. University of Texas Health Science Center at San Antonio, School of Medicine, 7703 Floyd Curl Drive, San Antonio, TX 78299, United States;1. Key Laboratory of Interfacial Physics and Technology, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China;2. Key Laboratory for Colloid and Interface Chemistry, Key Laboratory of Special Aggregated Materials, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, Shandong, China;1. Punjab Technical University, Kapurthala, Punjab, India;2. Shaheed Bhagat Singh College of Engineering & Technology, Ferozpur, Punjab, India;3. Guru Nanak Dev University, Regional Campus, Jalandhar, Punjab 144007, India;4. ASB Industries Inc., 1031, Lambert Street, Barberton, OH 44203, USA |
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| Abstract: | The binding of progesterone by the cytosol fraction of rat myometrium during pregnancy and by the cytosol and 20,000g supernatant fraction of human myometrium in late pregnancy has been determined by a competitive protein-binding method and by equilibrium dialysis.In rat myometrium two kinds of progesterone binding components were observed: a non-specific binder resembling corticosteroid-binding globulin (CBG) and a progesterone-specific receptor. The relative amount of the specific receptor reaches a min. in mid-pregnancy and a max. before parturition, at a time when the non-specific binder is below the limit of detectability. The CBG-like binder reappears at least 2 days post partum.The total binding-site concn. of progesterone in the cytosol of rat myometrium during pregnancy was 1.1–6.0 pmol/mg of cytosol protein, being highest in mid-pregnancy and lowest during the last third of pregnancy and remaining so until 2 days post partum. The association constant of the specific progester-one receptor was ∼ 1.0 × 108 M−1.In human myometrium of late pregnancy a progesterone-binding component of high affinity and limited capacity was found. The binder was not specific for progesterone. It resembled the CBG-like binder of rat myometrium. The association constant was ∼ 1.0 × 109 M−1. The binding-site concn. for progesterone in the cytosol of human myometrium during late pregnancy was 2.3 ± 0.3 pmol/mg of cytosol protein in myometrium samples obtained from elective caesarian sections and 0.6 and 0.9 pmol/mg of cytosol protein in two samples obtained during labour. |
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