title: Progesterone induces transient changes in plasma membrane fluidity of amphibian oocytes during the first meiotic division.
abstract: Progesterone acts at the surface of the amphibian oocyte to induce resumption of the meiotic divisions. Progesterone binding leads to a transient dose-dependent decrease in the fluidity (increase in order parameter) of the Rana oocyte plasma membrane, which was detected by electron spin resonance in isolated plasma membranes using either 5- or 16-DOXYL stearic acid probes. The 5-DOXYL probe, which inserts into the membrane with the spin label nearest the surface, showed an increase in the order parameter within minutes, a maximum change by 2 h, and a return to control levels by 6 h. The order parameter for the 16-DOXYL probe, which reflects the fluidity deeper within the plasma membrane, increased slowly and remained elevated during the first meiotic division. RU 38486, a synthetic steroid that blocks progesterone receptors, prevents progesterone-induced fluidity changes. These findings indicate that the binding of progesterone to its receptor changes the oocyte plasma membrane structure resulting in a differential decrease in mobility near the membrane surface compared to that deeper in the membrane.
authors.affiliation: Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461.
authors.forename: G A
authors.initials: GA
authors.lastname: Morrill
authors.forename: K
authors.initials: K
authors.lastname: Doi
authors.forename: A B
authors.initials: AB
authors.lastname: Kostellow
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008540:Meiosis / Q000187:drug effects; D008560:Membrane Fluidity / Q000187:drug effects*; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology*; D011898:Ranidae
chemical_list: D011374:Progesterone