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      Rapid effects of progesterone on ciliary beat frequency in the mouse fallopian tube

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          Abstract

          Background

          The physiological regulation of ciliary beat frequency (CBF) within the fallopian tube is important for controlling the transport of gametes and the fertilized ovum. Progesterone influences gamete transport in the fallopian tube of several mammalian species. In fallopian tubes isolated from cows, treatment with 20 micromolar progesterone caused a rapid reduction of the tubal CBF. The aims of this study were to establish methodology for studying fallopian tube CBF in the mouse, as it is an important model species, and to investigate if progesterone rapidly affects the CBF of mice at nM concentrations.

          Methods

          A method to assess tubal CBF of mice was developed. Fallopian tubes were dissected and the tissue was cut in small pieces. Tissue samples with moving cilia were located under an inverted bright field microscope and held still against the bottom of a petri dish by a motorized needle system. Images were acquired over 90 minutes at 35 degrees C with a high-speed camera and used for assessing changes in the CBF in response to the addition of hormone.

          Results

          The baseline CBF of the mouse fallopian tube was 23.3 +/- 3.8 Hz. The CBF was stable over at least 90 minutes allowing establishment of a baseline frequency, addition of hormone and subsequent recordings. Progesterone at concentrations of 20 micromolar and 100 nM significantly reduced the CBF by 10% and 15% respectively after 30 minutes compared with controls.

          Conclusions

          The present study demonstrates that the mouse, despite its small size, is a useful model for studying the fallopian tube CBF ex vivo. The rapid reduction in CBF by 100 nM progesterone suggests that gamete transport in the fallopian tube could be mediated by progesterone via a non-genomic receptor mechanism.

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          Most cited references 46

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          Cloning, expression, and characterization of a membrane progestin receptor and evidence it is an intermediary in meiotic maturation of fish oocytes.

          The structures of membrane receptors mediating rapid, nongenomic actions of steroids have not been identified. We describe the cloning of a cDNA from spotted seatrout ovaries encoding a protein that satisfies the following seven criteria for its designation as a steroid membrane receptor: plausible structure, tissue specificity, cellular distribution, steroid binding, signal transduction, hormonal regulation, and biological relevance. For plausible structure, computer modeling predicts that the protein has seven transmembrane domains, typical of G protein-coupled receptors. The mRNA (4.0 kb) is only detected in the brain and reproductive tissues on Northern blots. Antisera only detect the protein (40 kDa) in plasma membranes of reproductive tissues. The recombinant protein produced in an Escherichia coli expression system has a high affinity (K(d) = 30 nM), saturable, displaceable, single binding site specific for progestins. Progestins alter signal transduction pathways, activating mitogen-activated protein kinase and inhibiting adenylyl cyclase, in a transfected mammalian cell line. Inhibition of adenylyl cyclase is pertussis toxin sensitive, suggesting the receptor may be coupled to an inhibitory G protein. Progestins and gonadotropin up-regulate both mRNA and protein levels in seatrout ovaries. Changes in receptor abundance in response to hormones and at various stages of oocyte development, its probable coupling to an inhibitory G protein and inhibition of progestin induction of oocyte maturation upon microinjection of antisense oligonucleotides are consistent with the identity of the receptor as an intermediary in oocyte maturation. These characteristics suggest the fish protein is a membrane progestin receptor mediating a "nonclassical" action of progestins to induce oocyte maturation in fish.
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            Identification, classification, and partial characterization of genes in humans and other vertebrates homologous to a fish membrane progestin receptor.

            Recently we discovered a previously uncharacterized gene with the characteristics of a membrane progestin receptor (mPR) in a fish model, spotted seatrout. Here, we report the identification, cloning, and characteristics of other members of this hitherto unknown family of putative mPRs from several vertebrate species, including human, mouse, pig, Xenopus, zebrafish, and Fugu, with highly conserved nucleotide and deduced amino acid sequences and similar structures to the spotted seatrout mPR. The 13 vertebrate genes identified seem to belong to an unknown gene family. Phylogenetic analysis indicates these cDNAs comprise three distinct groups (named alpha, beta, and gamma) within this gene family. Structural analyses of the translated cDNAs suggest they encode membrane proteins with seven transmembrane domains. The transcript sizes of the human alpha, beta, and gamma putative mPR mRNAs varied from 2.8 to 5.8 kb and showed distinct distributions in reproductive, neural, kidney and intestinal tissues, respectively. Recombinant human alpha, gamma, and mouse beta proteins produced in an Escherichia coli expression system demonstrated high affinity (K(d) = 20-30 nM) saturable binding for progesterone. Further analysis of binding to the gamma-subtype revealed binding was specific for progestins and was displaceable, with rapid rates of association and dissociation (t(1/2) = 2-8 min). These results suggest this is a new family of steroid receptors unrelated to nuclear steroid receptors, but instead having characteristics of G protein-coupled receptors.
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              Progesterone signaling in human myometrium through two novel membrane G protein-coupled receptors: potential role in functional progesterone withdrawal at term.

              Progestin withdrawal is a crucial event for the onset of labor in many mammalian species. However, in humans the mechanism of a functional progestin withdrawal is unclear, because progestin concentrations do not drop in maternal plasma preceding labor. We report the presence of two novel functional membrane progestin receptors (mPRs), mPRalpha and mPRbeta, in human myometrium that are differentially modulated during labor and by steroids in vitro. The mPRs are coupled to inhibitory G proteins, resulting in a decline in cAMP levels and increased phosphorylation of myosin light chain, both of which facilitate myometrial contraction. Activation of mPRs leads to transactivation of PR-B, the first evidence for cross-talk between membrane and nuclear PRs. Progesterone activation of the mPRs leads also to a decrease of the steroid receptor coactivator 2. Our data indicate the presence of a novel signaling pathway mediated by mPRs that may result in a functional progestin withdrawal, shifting the balance from a quiescent state to one of contraction.
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                Author and article information

                Journal
                Reprod Biol Endocrinol
                Reproductive Biology and Endocrinology : RB&E
                BioMed Central
                1477-7827
                2010
                15 May 2010
                : 8
                : 48
                Affiliations
                [1 ]Institute of Neuroscience and Physiology, the Sahlgrenska Academy, University of Gothenburg, SE-405 30 Göteborg, Sweden
                [2 ]Department of Physics, University of Gothenburg, SE-412 96 Göteborg, Sweden
                Article
                1477-7827-8-48
                10.1186/1477-7827-8-48
                2887877
                20470431
                Copyright ©2010 Bylander et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Categories
                Methodology

                Human biology

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