Identification of G-protein α-subunits in ovaries

Abstract

The presence of G-protein ~-subunits in somatic ovarian cells of albino rats and changes in their distribution during follicle maturation are demonstrated. A possible role of these proteins in signal transduction to ovarian structures is discussed.Key Words: ovary; folliculocyte; thecocyte; ~-subunit; G-protein Function of all cells, tissues, and organs is subjected to neurohumoral regulation. Humoral factors play an outstanding role in the regulation of female reproductive organs, since cyclic morphofunctional reorganization in these organs and changes directed toward conception are strictly controlled by the hypothalamo-hypophyseal system. This classic scheme of gonadotropin-mediated humoral regulation has been recently supplemented by a discovery of a great number of humoral modulators of this system (thyroid hormones, adrenocorticotropic hormone, insulin, etc.).Delicate mechanisms mediating the action of hormonal stimuli on effector cells in reproductive organs, in particular, cells of ovarian follicles, representing an oocyte microenvironment, remain poorly understood. Evaluation of the role of G-proteins, members of the GTPase superfamily, is a promising direction ha the study of signal transduction system in the ovarian-follicular assembly. There is evidence that GTPases act as transmitters in the interactions between receptor proteins and intracellular target enzymes [1-81.G-Proteins are a peculiar group of peripheral cytoplasmic proteins belonging to high-affinity GTPases, consisting of three subunits (0~, [3, and ?). The active center of the molecule is formed by 0c-subunits. High-affinity binding and hydrolysis of GTP molecule in the active center is accompanied by its inactivation, which affects its interactions with Department of Histology and Embryology, Pediatric Faculty of the Russian State Medical University, Moscow other macmmolecules and modulates general and specific cellular processes. There are known different forms of G-proteins mediating both activating and inhibiting hormonal stimuli to the cell effector systems. These differences are determined by their c~-subunits.Study of G-protein ~-subunits and their possible role in hormonal signal transduction to target cells in ovarian follicles can substantially supplement the fundamental theory of follicular selection.Our objective was to visualize and investigate the distribution of G-proteins in developing ovarian follicles. MATERIALS AND METHODSOvaries of mature albino random-bred rats were studied. Cryosections (7-~t thick) of ovaries were slightly dried at room temperature, fixed in absolute acetone for 10 min, and washed with 10 mM phosphate buffer (pH 7.6) containing 0.5 M NaC1 and 1% Tween-20. Polyclonal rabbit immunoglobulin to G-protein ~-subunit served as primary antibodies. Bound primary antibody were visualized usinz the avidin-biotin-peroxidase complex.In order to verify the specificity of the reaction control sections were not incubated with primary antibodies. Microscopy and photography was performed using an Opton microscope....