ROLE OF CYCLIC AMP IN OOCYTE MATURATION AND GLYCOLYSIS IN THE PRE-OVULATORY RAT FOLLICLE

1978 ◽  
Vol 87 (2) ◽  
pp. 377-388 ◽  
Author(s):  
Torbjörn Hillensjö ◽  
Carl Ekholm ◽  
Kurt Ahrén
Keyword(s):  
Cyclic Amp ◽  
Oocyte Maturation ◽  
Lactate Production ◽  
Phosphodiesterase Inhibitor ◽  
Follicular Development ◽  
Phosphodiesterase Inhibitors ◽  
Defined Medium ◽  
High Concentration ◽  
Stimulatory Action

ABSTRACT This study was undertaken in order to analyse the role of cyclic AMP (cAMP) in the stimulatory action of LH on the resumption of oocyte meiosis (oocyte maturation) and follicular glycolysis. Follicular development was induced in immature rats by a single injection of pregnant mares' serum gonadotrophin. Pr-ovulatry follices were extirpated on the day before ovulation and incubated in a chemically defined medium for 4–10 h. The follicle-enclosed oocytes remained in the dictyate stage when incubated in hormone-free medium but in the presence of LH oocyte maturation was induced. When cAMP or butyryl derivatives of cAMP were added to the incubation medium no effect on the oocyte was seen. However, these nucleotides prevented the stimulatory action of LH on the oocytes. The phosphodiesterase inhibitors theophylline and IBMX had similar effects as cAMP on oocyte maturation, causing a reversible blockage of the LH effect. When 8-Br-cAMP and the phosphodiesterase inhibitor ICI 63.197 were tested it was found that both had inherent stimulatory effects on oocyte maturation at certain concentrations. Pre-incubation of the follicles in a high concentration of dibutyryl cAMP followed by transfer to plain medium resulted in oocyte maturation. Follicular lactate production was stimulated by all cyclic nucleotide derivatives tested, except cAMP, and by IBMX and ICI 63.197. There was no reduction by these agents of the stimulatory effect of LH on lactate production. A model to explain the role of cAMP in oocyte maturation is presented.

Forskolin and phosphodiesterase inhibitors release adenosine but inhibit morphine-evoked release of adenosine from spinal cord synaptosomes

1991 ◽  
Vol 69 (6) ◽  
pp. 877-885 ◽  
Author(s):  
D. Nicholson ◽  
T. D. White ◽  
J. Sawynok
Keyword(s):  
Spinal Cord ◽  
Cyclic Amp ◽  
Phosphodiesterase Inhibitor ◽  
Phosphodiesterase Inhibitors ◽  
Dorsal Spinal Cord ◽  
Adenosine Release ◽  
Basal Release ◽  
Phosphodiesterase Isoenzymes ◽  
Dorsal Spinal ◽  
Ventral Spinal Cord

The effects of forskolin, Ro 20-1724, rolipram, and 3-isobutyl-1-methylxanthine (IBMX) on morphine-evoked release of adenosine from dorsal spinal cord synaptosomes were evaluated to examine the potential involvement of cyclic AMP in this action of morphine. Ro 20-1724 (1–100 μM), rolipram (1–100 μM), and forskolin (1–10 μM) increased basal release of adenosine, and at 1 μM inhibited morphine-evoked release of adenosine. Release of adenosine by Ro 20-1724, rolipram, and forskolin was reduced 42–77% in the presence of α, β-methylene ADP and GMP, which inhibits ecto-5′-nucleotidase activity by 81%, indicating that this adenosine originated predominantly as nucleotide(s). Significant amounts of adenosine also were released from the ventral spinal cord by these agents. Ro 20-1724 and rolipram did not significantly alter the uptake of adenosine into synaptosomes. Although Ro 20-1724 and rolipram had only limited effects on the extrasynaptosomal conversion of added cyclic AMP to adenosine, IBMX, a phosphodiesterase inhibitor with a broader spectrum of inhibitory activity for phosphodiesterase isoenzymes, significantly inhibited the conversion of cyclic AMP to adenosine and resulted in recovery of a substantial amount of cyclic AMP. As with the non-xanthine phosphodiesterase inhibitors, IBMX increased basal release of adenosine and reduced morphine-evoked release of adenosine. Adenosine released by IBMX was reduced 70% in the presence of α, β-methylene ADP and GMP, and release from the ventral spinal cord was 61% of that from the dorsal spinal cord. Collectively, these results indicate that forskolin and phosphodiesterase inhibitors release nucleotide(s) which is (are) converted extrasynaptosomally to adenosine. For forskolin, Ro 20-1724, and rolipram, the nucleotide released could be cyclic AMP. Morphine releases adenosine per se, and forskolin and phosphodiesterase inhibitors reduce this release. The lack of increase in the action of morphine with phosphodiesterase inhibitors in particular does not support a role for stimulation of cyclic AMP production by morphine in the release of adenosine. The reduction in morphine-evoked release of adenosine by forskolin and phosphodiesterase inhibitors suggests either (a) that a reduction in cyclic levels by morphine promotes adenosine release, or (b) that cyclic AMP interferes with the release process.Key words: forskolin, Ro 20-1724, 3-isobutyl-1-methylxanthine, cyclic AMP, morphine, adenosine release, spinal cord.

scholarly journals The Role of Androgens in Mammals Folliculogenesis

2018 ◽  
Vol 44 (1) ◽  
pp. 15
Author(s):  
Livia Brunetti Apolloni ◽  
Jamily Bezerra Bruno ◽  
Benner Geraldo Alves ◽  
José Ricardo de Figueiredo
Keyword(s):  
Androgen Receptor ◽  
In Vitro Culture ◽  
Steroid Hormones ◽  
Oocyte Maturation ◽  
Follicular Development ◽  
Follicular Growth ◽  
Preantral Follicles ◽  
Ovarian Cells

Introduction: Steroid hormones production is a physiological process termed steroidogenesis. An important stage of this process is the conversion of androgens into estrogens through aromatase enzyme. Furthermore, androgens are important in the process of folliculogenesis, promoting follicular growth in different species. Thus, the aim of this review was to present the process of synthesis, mechanism of action, and importance of androgens in folliculogenesis. Additionally, the main results of in vitro culture of ovarian cells in the presence of these hormones were emphasized.Review: Folliculogenesis begins in prenatal life in most of species and can be defined as the process of formation, follicular growth, and oocyte maturation. Preantral follicles represent 95% of the follicular population and assisted reproductive technologies have been developed (e.g., Manipulation of Oocytes Enclosed in Preantral Follicles - MOEPF) in order to avoid the great follicle loss that occurs naturally in vivo by atresia. The MOEPF aim to obtain a large number of competent oocytes from preantral follicles and then subject to in vitro maturation, fertilization, and culture for embryo production. However, the development of an efficient medium to ensure the follicular survival and oocyte maturation is the major challenge of this biotechnology. To achieve the success on in vitro culture, the effects of substances as androgens on follicular development have been evaluated. Androgens are steroid hormones produced in theca cells (TC) that are fundamental for follicular growth. These cells provide all the androgens required by the developing follicles for conversion into estrogens by the granulosa cells (GC). Androgens receptors (AR) are localized in cell cytoplasm of all follicular categories, being more expressed in preantral follicles. The androgen pathway initiates through its connection to its receptor, making a complex androgen-AR, that in the nucleus helps on the process of gene transcription related with follicular survival. This mechanism is androgen receptor genomic activity. In addition to genomic action, there is an androgen receptor non-genomic activity. This occurs through activation of AR and its interaction with different signaling molecules located on the cell membrane, triggering events that aid in the follicular development. Regardless of the androgens actions, ovarian cells of several species subjected to in vitro culture have shown the importance of these hormones on the follicle development. Recent studies demonstrated that androgens addition on the culture medium stimulated the activation of preantral follicles (bovine and caprine), antrum formation (swine), survival (non-primate), and oocyte maturation (antral follicles; bovine). Also, some studies suggest that the addition of these hormones on in vitro culture is dose-dependent and species-specific.Conclusion: This review shows the role of androgens in different stages of follicular development and its action as a substrate for steroidogenesis and transcription of genes related to follicular survival and oocyte maturation. However, when these hormones should be added during in vitro follicular culture and which concentration is required remains unclear, being necessary more studies to elucidate these aspects.

scholarly journals The Role of Cyclic Nucleotides in the CNS

1977 ◽  
Vol 4 (3) ◽  
pp. 151-195 ◽  
Author(s):  
John W. Phillis
Keyword(s):  
Cyclic Amp ◽  
Synaptic Transmission ◽  
Cyclic Gmp ◽  
Adenosine Receptor ◽  
Cyclic Nucleotides ◽  
Phosphodiesterase Inhibitors ◽  
Adenosine Uptake ◽  
Injection Techniques ◽  
Firm Basis

SUMMARY:On the basis of the information presented in this review, it is difficult to reach any firm decision regarding the role of cyclic AMP (or cyclic GMP) in synaptic transmission in the brain. While it is clear that cyclic nucleotide levels can be altered by the exposure of neural tissues to various neurotransmitters, it would be premature to claim that these nucleotides are, or are not, essential to the transmission process in the pre- or postsynaptic components of the synapse. In future experiments with cyclic AMP it will be necessary to consider more critically whether the extracellularly applied nucleotide merely provides a source of adenosine and is thus activating an extracellularly located adenosine receptor, or whether it is actually reaching the hypothetical sites at which it might act as a second messenger. The application of cyclic AMP by intracellular injection techniques should minimize this particular problem, although possibly at the expense of new difficulties. Prior blockade of the adenosine receptor with agents such as theophylline or adenine xylofuranoside may also assist in the categorization of responses to extracellularly applied cyclic AMP as being a result either of activation of the adenosine receptor or of some other mechanism. Ultimately, the development of highly specific inhibitors for adenylate cyclase should provide a firm basis from which to draw conclusions about the role of cyclic AMP in synaptic transmission. Similar considerations apply to the actions of cyclic GMP and the role of its synthesizing enzyme, guanylale cyclase.The use of phosphodiesterase inhibitors in studies on cyclic nucleotides must also be approached with caution. The diverse actions of many of these compounds, which include calcium mobilization and block of adenosine uptake, could account for many of the results that have been reported in the literature.

scholarly journals Receptor-mediated gonadotropin action in the ovary. Regulatory role of cyclic nucleotide phosphodiesterase(s) in intracellular adenosine 3′:5′-cyclic monophosphate turnover and gonadotropin-stimulated progesterone production by rat ovarian cells

1979 ◽  
Vol 180 (1) ◽  
pp. 201-211 ◽  
Author(s):  
Salman Azhar ◽  
K. M. Jairam Menon
Keyword(s):  
Cyclic Amp ◽  
Kinase Activity ◽  
Phosphodiesterase Inhibitors ◽  
Protein Kinase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Steroid Production ◽  
Progesterone Production ◽  
Ovarian Cells ◽  
Cyclic Amp Accumulation

The regulatory role of cyclic nucleotide phosphodiesterase(s) and cyclic AMP metabolism in relation to progesterone production by gonadotropins has been studied in isolated rat ovarian cells. Low concentrations of choriogonadotropin (0.4–5ng/ml) increased steroid production without any detectable increase in cyclic AMP, when experiments were carried out in the absence of phosphodiesterase inhibitors. The concentration of choriogonadotropin (10ng/ml) that stimulated progesterone synthesis maximally resulted in a minimal increase in cyclic AMP accumulation and choriogonadotropin binding. Choriogonadotropin at a concentration of 10ng/ml and higher, however, significantly stimulated protein kinase activity and reached a maximum between 250 and 1000ng of hormone/ml. Higher concentrations (50–2500ng/ml) of choriogonadotropin caused an increase in endogenous cyclic AMP, and this increase preceded the increase in steroid synthesis. Analysis of dose–response relationships of gonadotropin-stimulated cyclic AMP accumulation, progesterone production and protein kinase activity revealed a correlation between these responses over a wide concentration range when experiments were performed in the presence of 3-isobutyl-1-methylxanthine. The phosphodiesterase inhibitors papaverine, theophylline and 3-isobutyl-1-methylxanthine each stimulated steroid production in a dose-dependent manner. Incubation of ovarian cells with dibutyryl cyclic AMP or 8-bromo cyclic AMP mimicked the steroidogenic action of gonadotropins and this effect was dependent on both incubation time and nucleotide concentration. Maximum stimulation was obtained with 2mm-dibutyryl cyclic AMP and 8-bromo cyclic AMP, and this increase was close to that produced by a maximally stimulating dose of choriogonadotropin. Other 8-substituted derivatives such as 8-hydroxy cyclic AMP and 8-isopropylthio cyclic AMP, which were less susceptible to phosphodiesterase action, also effectively stimulated steroidogenesis. The uptake and metabolism of cyclic [3H]AMP in ovarian cells was also studied in relation to steroidogenesis. When ovarian cells were incubated for 2h in the presence of increasing concentrations of cyclic [3H]AMP, the radioactivity associated with the cells increased almost linearly up to 250μm-cyclic [3H]AMP concentration in the incubation medium. The 3H label in the cellular extract was recovered mainly in the forms ATP, ADP, AMP, adenosine and inosine, with cyclic AMP accounting for less than 1% of the total tissue radioactivity. Incubation of cyclic AMP in vitro with ovarian cells resulted in a rapid breakdown of the nucleotide in the medium. The degradation products in the medium have been identified as AMP, adenosine and inosine. The rapid degradation of cyclic AMP by phosphodiesterase(s) makes it difficult to correlate changes in cyclic AMP concentrations with steroidogenesis. These observations thus provide an explanation for the previously observed lack of cyclic AMP accumulation under conditions in which low doses of choriogonadotropin stimulated steroidogenesis without any detectable changes in cyclic AMP accumulation.

scholarly journals Resensitization of hepatocyte glucagon-stimulated adenylate cyclase can be inhibited when cyclic AMP phosphodiesterase inhibitors are used to elevate intracellular cyclic AMP concentrations to supraphysiological values

1988 ◽  
Vol 249 (2) ◽  
pp. 543-547 ◽  
Author(s):  
G J Murphy ◽  
M D Houslay
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Phosphodiesterase Inhibitor ◽  
Phosphodiesterase Inhibitors ◽  
Maximal Effect ◽  
Cyclic Amp Phosphodiesterase ◽  
Dose Dependent Fashion ◽  
Independent Process ◽  
Pre Treatment ◽  
Dose Dependent

Treatment of intact hepatocytes with glucagon led to the rapid desensitization of adenylate cyclase, which reached a maximum around 5 min after application of glucagon, after which resensitization ensued. Complete resensitization occurred some 20 min after the addition of glucagon. In hepatocytes which had been preincubated with the cyclic AMP phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), glucagon elicited a stable desensitized state where resensitization failed to occur even 20 min after exposure of hepatocytes to glucagon. Treatment with IBMX alone did not elicit desensitization. The action of IBMX in stabilizing the glucagon-mediated desensitized state was mimicked by the non-methylxanthine cyclic AMP phosphodiesterase inhibitor Ro-20-1724 [4-(3-butoxy-4-methoxylbenzyl)-2-imidazolidinone]. IBMX inhibited the resensitization process in a dose-dependent fashion with an EC50 (concn. giving 50% of maximal effect) of 26 +/- 5 microM, which was similar to the EC50 value of 22 +/- 6 microM observed for the ability of IBMX to augment the glucagon-stimulated rise in intracellular cyclic AMP concentrations. Pre-treatment of hepatocytes with IBMX did not alter the ability of either angiotensin or the glucagon analogue TH-glucagon, ligands which did not increase intracellular cyclic AMP concentrations, to cause the rapid desensitization and subsequent resensitization of adenylate cyclase. It is suggested that, although desensitization of glucagon-stimulated adenylate cyclase is elicited by a cyclic AMP-independent process, the resensitization of adenylate cyclase can be inhibited by a process which is dependent on elevated cyclic AMP concentrations. This action can be detected by attenuating the degradation of cyclic AMP by using inhibitors of cyclic AMP phosphodiesterase.

The Role of Cyclic AMP in the Octopaminergic Modulation of Flight Muscle in the Locust

1991 ◽  
Vol 161 (1) ◽  
pp. 423-438
Author(s):  
MATTHEW D. WHIM ◽  
PETER D. EVANS
Keyword(s):  
Cyclic Amp ◽  
Flight Muscle ◽  
Schistocerca Gregaria ◽  
Phosphodiesterase Inhibitors ◽  
Motor Units ◽  
Blocking Agent ◽  
Receptor Activation ◽  
Octopamine Receptors ◽  
Flight Muscles

The role of cyclic AMP in the octopaminergic modulation of the dorsal longitudinal flight muscles of the locust Schistocerca gregaria has been investigated. Several techniques have been used to elevate cyclic AMP levels in this tissue by mechanisms that bypass the receptor activation stage. These include the use of phosphodiesterase inhibitors to block the metabolism of cyclic nucleotides, the use of forskolin, the diterpene activator of adenylate cyclase, and the direct application of permeable and phosphodiesterase-resistant analogues of cyclic AMP. All these approaches can be shown to mimic the modulatory effects of octopamine on the flight muscle. Surprisingly, the phosphodiesterase inhibitors used were not able to potentiate the actions of octopamine on this preparation. Octopamine increases cyclic AMP levels in a similar fashion in all five motor units of this muscle, an effect that is selectively blocked by phentolamine, an α-adrenergic blocking agent that blocks octopamine receptors in other preparations. In addition, stimulation of the dorsal unpaired median neurone to the dorsal longitudinal flight muscles (DUMDL) results in a frequency-dependent increase in cyclic AMP levels in the muscle that is also blocked by phentolamine. The data presented suggest that the octopamine-mediated modulation of neurally evoked tension in this muscle is brought about by a mechanism that involves an increase in cyclic AMP levels in the tissue.

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