Plasma prostaglandin F2 alpha and reproduction in the female Triturus carnifex (Laur.).

Plasma patterns of prostaglandin F2 alpha (PGF2 alpha) and sex hormones (progesterone, androgens and 17 beta-estradiol) have been studied in the female crested newt, Triturus carnifex (Laur.), during the annual sexual cycle. The effects of exogenous PGF2 alpha on sex hormones were determined. In addition, the effects of one week's captivity on plasma PGF2 alpha and sex hormones were reported. PGF2 alpha plasma level peaked in April, was low in summer, and progressively increased during the autumn to peak again in December. The April PGF2 alpha coincided with a 17 beta-estradiol rise, and with a progesterone drop. The autumn PGF2 alpha increase was coupled to a 17 beta-estradiol rise, and therefore it has been tentatively related to ovary and oviduct development. In newts collected in April, moreover, a PGF2 alpha-dependent 17 beta-estradiol synthesis could occur, since PGF2 alpha injection induced a significant 17 beta-estradiol plasma increase. These findings led us to suppose that PGF2 alpha intervenes in spring breeding season termination through the induction of a 17 beta-estradiol synthesis as in other amphibian species. PGF2 alpha injection caused a progesterone decrease, probably by inducing corpora lutea lysis. The patterns of plasma sex hormones were consistent with the results reported for the same newt species.     

Plasma prostaglandin F2 alpha in the male Triturus carnifex (Laur.) during the reproductive annual cycle and effects of exogenous prostaglandin on sex hormones

Plasma patterns of prostaglandin F2 alpha (PGF2 alpha) and sex hormones (progesterone, androgens and 17 beta-estradiol) have been studied in the male crested newt, Triturus carnifex (Laur.), during the sexual cycle. The effects of exogenous PGF2 alpha on sex steroids have also been observed. In addition, effects of one week's captivity are reported. The patterns of plasma sex hormones, during the annual cycle, are consistent with the results previously reported for the same newt species. PGF2 alpha plasma level peaks in April, is low in summer, and progressively increases during autumn to peak again in December. The April PGF2 alpha peak coincides with a plasma estradiol increase and with an androgens drop. In April-collected newts, moreover, PGF2 alpha treatment induces a significant estradiol increase. These findings lead us to suppose that at the end of the breeding season (April) a PGF2 alpha-dependent estradiol synthesis occurs which could be implied in reproductive period termination. In several vertebrates, including some amphibian species, in fact, chronic administration of estradiol results in a strong inhibition of testicular endocrine tissue activity. The putative role of PGF2 alpha-dependent estradiol production in the gonadal regulation in amphibia living in temperate zones is discussed. The autumn PGF2 alpha increase has been tentatively related to the recovery gonadal processes and secondary sexual character development.     

PGF2 alpha and breathing pattern in newborn pigs

The effect of PGF2 alpha has been evaluated in 11 unanaesthetized unrestrained piglets and in 3 anaesthetized piglets (2-3 days old) using a barometric-plethysmographic technique. PGF2 alpha (mg 0.25/pig) was administered as aerosol for 5 min. In 3 of the unanaesthetized newborn pigs the effect of PGF2 alpha aerosol has been evaluated after indomethacin (mg 1/Kg i.v.). The vagal dependent activity of the prostaglandin was also evaluated after atropine (mg 0.08/Kg i.m.). Our results show that PGF2 alpha in newborn pigs causes hypoventilation due to a decrease in respiratory rate and to a lengthening in TE. The changes in TE are due to an increase in the incidence and duration of apneic events characterizing the respiratory activity at birth. After indomethacin PGF2 alpha does not change the breathing pattern. Atropine only partially reduces the effects of PGF2 alpha while, after anaesthesia, prostaglandin does not change the breathing pattern. Consequently our results show that PGF2 alpha in newborn animals similar to other prostaglandins acts as a depressant of respiratory activity.     

Plasma prostaglandin F2α in the male triturus carnifex (Laur.) during the reproductive annual cycle and effects of exogenous prostaglandin on sex hormones

Plasma patterns of prostaglandin F2α (PGF2α) and sex hormones (progesterone, androgens and 17ß-estradiol) have been studied in the male crested newt, Triturus carnifex (Laur.), during the sexual cycle. The effects of exogenous PGF2α on sex steroids have also been observed. In addition, effects of one week's captivity are reported. The patterns of plasma sex hormones, during the annual cycle, are consistent with the results previously reported for the same newt species. PGF2α plasma level peaks in April, is low in summer, and progressively increases during autumn to peak again in December. The April PGF2α peak coincides with a plasma estradiol increase and with an adrogens drop. In April-collected newts, moreover, PGF2α treatment induces a significant estradiol increase. These findings lead us to suppose that at the end of the breeding season (April) a PGF2α-dependent estradiol synthesis occurs which could be implied in reproductive peroid termination. In several vertebrates, including some amphibian species, in fact, chronic administration of estradiol results in a strong inhibition of testicular endocrine tissue activity. The putative role of PGF2α-dependent estradiol production in the gonadal regulation in amphibia living in temperate zones is discussed. The autumn PGF2α increase has been tentatively related to the recovery gonadal processes and secondary sexual character development.     

In vitro insulin-like actions of the growth factor from the tapeworm, Spirometra mansonoides

In vitro actions of purified plerocercoid growth factor (PGF) were compared with those of insulin and human growth hormone (hGH) in adipose tissue from normal male rats. Insulin-like effects were measured by the ability of PGF, insulin, or hGH to stimulate oxidation of [U-14C]glucose to 14CO2, to stimulate lipogenesis, and to inhibit epinephrine-induced lipolysis. PGF and insulin stimulated significant increases in glucose oxidation and lipogenesis in adipose tissue that had not been preincubated as well as in tissue that had been preincubated. hGH stimulated insulin-like effects only in tissue that had been preincubated for 3 hr. Insulin, hGH, and PGF inhibited epinephrine-induced lipolysis of preincubated (3 hr) adipose tissue. hGH produced a dramatic lipolytic response in tissue freshly removed from normal rats but no dose of PGF was lipolytic. PGF did not displace 125I-insulin from its receptors on adipocytes but did competitively inhibit 125I-hGH binding to adipocytes. These results suggest that PGF has direct insulin-like actions which are initiated by binding a GH receptor, but PGF had no anti-insulin action and the insulin-like activity of PGF was unaffected by refractoriness of adipose tissue to GH.     

Reproduction in chinchilla (Chinchilla lanigera): current status of environmental control of gonadal activity and advances in reproductive techniques

In female swine, PGF2α is an important regulator of corpora luteal (CL) function, uterine contractility, ovulation, and embryo attachment. High affinity PGF2α receptors are present in the CL at all stages of the estrous cycle and they are functional. Therefore, a lack of luteolytic capacity of PGF2α is related to other factors that have not been well identified. In female pigs, a single exogenous PGF2α injection produces a short lasting decrease in plasma progesterone levels but does not induce luteolysis before day 12 of the estrous cycle. However, multiple injections of PGF2α can induce luteolysis before day 12 of the estrous cycle and may be utilized in the development of protocols for ovulation synchronization and timed AI. Most commonly, PGF2α is used for the induction of farrowing and so facilitation of cross fostering. Further, since PGF2α is a smooth muscle stimulant, treatment to stimulate myometrial contractions and uterine evacuation of residual products from parturition or infectious debris, may have beneficial effects on post-weaning fertility. Administration of PGF2α at the moment of insemination has been shown to improve reproductive performances when fertility is otherwise low, such as in sow under summer heat stress.     

Contrasting effects of prostaglandins E2 and F2 alpha on sensitivity of the human cough reflex.

Prostaglandins have been shown to influence the sensitivity of the cough reflex. To investigate putative mechanisms of this, we examined the effects of inhaled prostaglandins E2 (PGE2) and F2 alpha (PGF2 alpha) on human cough responses elicited by two challenges, low chloride solution and capsaicin, which may activate different neural pathways. Baseline cough challenges were followed after 2 h by five breaths of PGE2, PGF2 alpha, or citric acid as a control. Cough challenges were repeated after 1 min. Potentiation of capsaicin responses occurred after PGE2 (median increase 2 coughs/min, range 0-7, P less than 0.01) and PGF2 alpha (median increase 8 coughs/min, range -3 to 27, P less than 0.01) compared with control. The effect of PGF2 alpha was greater (P less than 0.05) than that of PGE2. Potentiation of low chloride responses also occurred after PGF2 alpha (median increase 7 coughs/2 min, range -1 to 19, P less than 0.01), but effects of PGE2 were insignificant against this challenge (median change -1 coughs/2 min, range -4 to 13). These data suggest that PGE2 and PGF2 alpha have different effects on the sensitivity of the human cough reflex, which may be relevant during airway disease.     

The effect of supplementation with n-6 polyunsaturated fatty acids on 1-, 2- and 3-series prostaglandin F production by ovine uterine epithelial cells

Linoleic acid (LA, 18:2n-6) has variously been found to increase or inhibit synthesis of 2-series prostaglandins (PGs), derived from arachidonic acid (AA, 20:4n-6). gamma-linolenic acid (GLA, 18:3n-6) containing oils are promoted to women for a variety of reproductive problems. Little is known concerning their actual effects on reproduction. We investigated the effects of LA, GLA and AA supplementation (25-100 microM) on basal and oxytocin (OT) stimulated production of 1-, 2- and-3 series PGs by uterine epithelial cells isolated from non-pregnant ewes, used as a model system to study endometrial PG production. PGF isomers were measured using radioimmunoassays following separation by high performance chromatography (HPLC). OT challenge increased the proportion of PGF2alpha in relation to PGF1alpha and PGF3alpha in control medium. LA supplementation decreased all PGF isomer production and reduced responsiveness to OT. GLA increased both absolute and proportional PGF1alpha production and slightly enhanced PGF2alpha generation. AA increased PGF2alpha generation and raised its isometric proportion. Both GLA and AA increased overall PGF output significantly but prevented the cells from responding to OT. These results suggest that consumption of LA and GLA are likely to differentially alter both uterine PG metabolism and responsiveness to OT. This may have implications for the control of a variety of reproductive processes.     

PGF2α synthesis in isolated cerebellar glomeruli: Effects of membrane depolarization, calcium availability and phospholipase activity

The controlling factors for PGF2 alpha production were assessed in isolated cerebellar glomeruli, since this prostaglandin has been shown to stimulate the release of neurotransmitters from the mossy fiber terminals associated with this synaptic preparation. The metabolism of PGE2 was also examined, in order to determine the specificity of any treatment effects. It was observed that K(+)-dependent membrane depolarization or the activation of voltage-sensitive Na+ channels with veratradine stimulated the production of PGF2 alpha. The syntheses of both prostanoids were dependent on available calcium and were blocked by cyclooxygenase inhibitors. The lipoxygenase inhibitor NDGA also reduced the accumulation of PGE2 and PGF2 alpha. In addition, PGF2 alpha synthesis was stimulated by the phospholipase A2 activator melittin and was reduced due to phospholipase inhibition with dibucaine. These results are consistent with a role for PGF2 alpha in the evoked release of neurotransmitter from cerebellar mossy fiber terminals.     

The effect of the prostaglandin F2alpha analogue ICI 81008 on uterine small arteries and on blood pressure.

The effects of PGF2alpha and its analogue ICI 81008 have been compared on the small arteries of the omentum uteri on the rat. The vessels measured 20-80 mum in diameter and were examined by intra-vital-microscopy. While the maximum responses of PGF2alpha and ICI 81008 were similar, the duration of the effect of ICI 81008 was significantly longer (P is less than 0.001). At 15 minutes after the administration of the drugs the effect of ICI 81008 was still almost maximal, while the PGF2alpha response disappeared.     

The role of omega-3 polyunsaturated fatty acids in reproduction of sheep and cattle

The positive effects of fat and energy supplementation on improvements in reproduction are well documented. However, the specific effects of omega-3 polyunsaturated fatty acids (n-3) on reproductive success in ruminants have not been examined in detail. While the link between n-3 and markers associated with reproduction, in particular, prostaglandin F(2α) (PGF(2α)) and the link between PGF(2α) and reproductive outcomes are well established, evidence of a direct effect of high n-3 diets on measurable reproductive outcomes in ruminants is lacking. Therefore, the aim of the current review was to examine the effect of n-3 on a number of reproductive markers and measurable outcomes in sheep and cattle. There is strong evidence linking consumption of diets high in n-3 with reduced circulating peripheral inflammatory markers such as PGF(2α). Inflammatory eicosanoids including PGF(2α), in particular, can significantly affect reproduction outcomes such as the onset of oestrus, embryo survival and parturition. While there is also evidence linking n-3 supplementation with longer time to oestrus and parturition associated with reduced PGF(2α), the effects of n-3 on other measurable outcomes of reproductive success, such as pregnancy rate, embryo survival and intergenerational effects on the health and production of offspring are largely unknown. Similarly, the effects of diets high in n-3 or n-6 polyunsaturated fatty acids on male fertility are also unknown.     

Recent reports about enzymes related to the synthesis of prostaglandin (PG) F(2) (PGF(2α) and 9α, 11β-PGF(2))

Prostaglandin (PG) F(2α) is widely distributed in various organs and exhibits various biological functions, such as luteolysis, parturition, aqueous humor homeostasis, vasoconstriction, rennin secretion, pulmonary fibrosis and so on. The first enzyme reported to synthesize PGF(2) was referred to as PGF synthase belonging to the aldo-keto reductase (AKR) 1C family, and later PGF(2α) synthases were isolated from protozoans and designated as members of the AKR5A family. In 2003, AKR1B5, which is highly expressed in bovine endometrium, was reported to have PGF(2α) synthase activity, and recently, the paper entitled 'Prostaglandin F(2α) synthase activities of AKR 1B1, 1B3 and 1B7' was reported by Kabututu et al. (J. Biochem.145, 161-168, 2009). Clones that had already been registered in a database as aldose reductases (AKR1B1, 1B3, and 1B7) were expressed in Escherichia coli, and these enzymes were found to have PGF(2α) synthase activity. Moreover, in the above-cited article, the effects of inhibitors specific for aldose reductase on the PGF(2α) synthase activity of AKR1B were discussed. Here, I present an overview of various PGF/PGF(2α) synthases including those of AKR1B subfamily that have been reported until now.     

Boar spermatozoa and prostaglandin F2alpha. Quality of boar sperm after the addition of prostaglandin F2alpha to the short-term extender over cooling time

Prostaglandin F(2alpha) (PGF(2alpha)) has been used to improve reproductive performance in swine. The goal of the present work was to determine how the addition of PGF(2alpha) affects boar sperm quality. Eleven different treatments were evaluated: eight with only PGF(2alpha) (0.625, 1.25, 2.50, 5, 10, 12.50, 25 and 50mg PGF(2alpha)/100ml) and three binary treatments (0.625mg PGF(2alpha)/100ml+200mug/ml hyaluronic acid (HA), 1.25mg PGF(2alpha)/100ml+200mug/ml HA, 0.625mg PGF(2alpha)/100ml+7.5muM caffeine (Caf)). All these substances were added to 16 ejaculates from 16 healthy and sexually mature boars (n=16), and each ejaculate was considered as a replicate. Our study also assessed the effects of these 11 treatments over different periods of preservation. Sperm quality was tested immediately after the addition of treatments (time 0), and after 1, 3, 6 and 10 days of cooling at 15 degrees C. To evaluate sperm quality, five parameters were analysed: (1) sperm viability, acrosome and mitochondrial sheath integrity (using a multiple fluorochrome-staining test), (2) sperm motility, (3) sperm morphology and (4) agglutination (using a computer assisted system) and (5) osmotic resistance (using the ORT). Parametric (analysis of variance for repeated measures) and non-parametric tests (Friedman test) were used as statistical analyses. Treatments with PGF(2alpha) concentrations higher than 12.5mg/100ml were cytotoxic while the others did not damage boar spermatozoa. Thus, the other treatments may be used to produce profitable effects without adverse effects. Moreover, the addition of PGF(2alpha) at 5mg/100ml to sperm diluted in BTS may maintain sperm viability and motility better after 6 days of cooling, because significant differences were observed (P<0.05) compared with control at the same time.     

Comparison of two dosages of prostaglandin F2a on canine uterine motility

The effect of 50 ug/kg prostaglandin F2a (PGF2a) was compared with 250 ug/kg PGF2a on uterine motility in the diestrous female. Microtipped pressure transducers were surgically implanted in the uteri of 6 females at 30 days diestrus and in 6 females at 60 days diestrus. Uterine responses to intravenous PGF2a (5 ug/kg), oxytocin (0.05 USP units/kg), and intramuscular PGF2a (50 ug/kg and 250 ug/kg) were measured in the awake females on Days 1 and 2 after implantation. There was no significant difference in the increase in intrauterine pressure produced by 50 ug/kg of PGF2a compared with 250 ug/kg of PGF2a. The longest duration of the effect occurred when 250 ug/kg of PGF2a were given. Side effects were also documented. Significantly more vomiting occurred when 250 ug/kg PGF2a were given than when 50 ug/kg PGF2a were administered. The only advantage to using a higher dosage of PGF2a appears to be the longer duration of motility.     

Interactions between prostaglandins E2 and F2alpha and isoprenalin in the dog heart in situ]

The effects of PGE2 and PGF2alpha on the isoprenaline induced elevation of myocardial contractility were studied on hearts of anesthetized dogs. The steady state effects were determined after single or simultaneous infusion of the substances. Two indices of contractility were used for the quantification of inotropic effects. PGE2 but not PGF2alpha showed positivinotropic effects. PGE2 significantly inhibited the inotropic responses induced by isoprenaline (p less than 0,01); whereas PGF2alpha was without any effect in this direction. The results are discussed with respect of a postjunctional action of PGE2.     

Actions of prostaglandins E1 and F2alpha on isolated intrapulmonary vascular smooth muscle.

The effects of PGE1 and PGF2alpha were studied on isolated strips of intrapulmonary arteries and veins from dog, sheep, swine and man. PGF2alpha contracted human arterial strips in a dose-dependent fashion, relaxed slightly sheep arteries and had no effect on dog arteries. Canine, sheep and human venous strips were contracted by PGF2alpha. PGE1 relaxed slightly both veins and arteries from dog and sheep. Human arteries usually contracted slightly and human veins usually relaxed slightly to PGE1. In a limited number of experiments, swine arteries and veins failed to respond to PGF2alpha or PGE1. All the vascular strips contracted well when exposed to NE. These results suggest that the responses of intrapulmonary vessels to PGF2alpha and PGE1 are species-dependent. PGF2alpha generally exhibits a contractile action, especially on veins. PGE1 usually relaxes intrapulmonary vessels. With regard to vessels from man, PGF2alpha is a powerful stimulant while PGE1 produces only small, variable effects.     

AKT-independent phosphorylation of TSC2 and activation of mTOR and ribosomal protein S6 kinase signaling by prostaglandin F2alpha

Prostaglandin F2alpha (PGF2alpha) is an important mediator of corpus luteum (CL) regression, although the cellular signaling events that mediate this process have not been clearly identified. It is established that PGF2alpha binds to a G-proteincoupled receptor (GPCR) to stimulate protein kinase C (PKC) and Raf-MEK-Erk signaling in luteal cells. The present experiments were performed to determine whether PGF2alpha stimulates the mammalian target of rapamycin (mTOR)/ribosomal protein S6 kinase 1 (S6K1) signaling pathway in steroidogenic luteal cells. We demonstrate that PGF2alpha treatment results in a timeand concentration-dependent stimulation of the phosphorylation and activation of S6K1. The stimulation of S6K1 in response to PGF2alpha treatment was abolished by the mTOR inhibitor rapamycin. Treatment with PGF2alpha did not increase AKT phosphorylation but increased the phosphorylation of Erk and the tumor suppressor protein tuberous sclerosis complex 2 (TSC2), an upstream regulator of mTOR. The effects of PGF2alpha were mimicked by the PKC activator PMA and inhibited by U0126, a MEK1 inhibitor. The activation of mTOR/S6K1 and putative down stream processes involving the translational apparatus (i.e. 4EBP1 phosphorylation, release of 4EBP1 binding in m(7)G cap binding assays, and the phosphorylation and synthesis of S6) were completely sensitive to treatment with rapamycin, implicating mTOR in the actions of PGF2alpha. Taken together, our data suggest that GPCR activation in response to PGF2alpha stimulates the mTOR pathway which increases the translational machinery in luteal cells. The translation of proteins under the control of mTOR may have implications for luteal development and regression and offer new strategies for therapeutic intervention in PGF2alpha-target tissues.     

Estradiol enhances prostaglandin synthase activity in epithelial but not in stromal cells of human endometrium

Exogenous estradiol (E2) has been shown to elevate PGF2 alpha output by explants of human secretory endometrium and in monolayer cultures of glandular epithelial, but not of stromal cells isolated from endometrium. In this study, PGF2 alpha output was measured in each of these cultures in the presence of E2 and the calcium ionophore A23187, added singly or in combination. The ionophore, known to liberate arachidonic acid (AA) by stimulating phospholipase activity, produced a calcium-dependent increase in PGF2 alpha output in the cultures of epithelial cells, whereas greater than additive effects were obtained with mixtures of E2 and A23187. In contrast, PGF2 alpha levels were not elevated by A23187 in the stromal cell cultures even in medium supplemented with CaCl2 or when E2 was added. A calcium-dependent increase in PGF2 alpha output was also observed in fragments of secretory endometrium incubated with A23187. Effects on PGF2 alpha output by endometrial fragments incubated with E2 and A23187 were essentially additive and intermediate between those of the two component cells types. Arachidonic acid produced similar increases in PGF2 alpha output in the epithelial and stromal cell cultures but only in the epithelial cell cultures was there greater utilization of AA in the presence of E2. When mixtures of E2 and AA were added to the cultures of epithelial cells the increase in PGF2 alpha output was 2.5-fold greater than the sum of the increases elicited by E2 or AA alone. In contrast, no enhancement of the AA effect by E2 was observed in the stromal cell cultures. Extrapolation of these results from cell cultures to intact tissue suggests that the epithelium and not the stroma is the primary target for the effects of E2 on PGF2 alpha output by secretory endometrium. The synergistic actions of E2 and either AA, the obligatory precursor of PGF2 alpha, or A23187, an enhancer of AA release from phospholipid stores, point to a stimulatory effect of E2 on prostaglandin synthase activity.     

Regulation of ANP secretion from isolated atria by prostaglandins and cyclooxygenase-2

Cyclooxygenase (COX) is a key enzyme regulating the production of various prostaglandins (PGs) from arachidonic acid. Angiotensin II has been reported to be an important inflammatory mediator, which increases COX-2. The aim of this study was to determine the role of various PGs and COX-2 in the regulation of atrial natriuretic peptide (ANP) secretion. PGF2α and PGD2 caused dose-dependent increases in ANP release and intra-atrial pressure. The potency for the stimulation of ANP secretion by PGF2α was higher than that by PGD2. In contrast, PGE2, PGI2, PGJ2, and thromboxane A2 did not show any significant effects. The increases in intra-atrial pressure and ANP secretion induced by PGF2α and PGD2 were significantly attenuated by the pretreatment with an inhibitor of PGF2α receptor. By the pretreatment with an inhibitor for phospholipase C (PLC), inositol 3-phosphate (IP3) receptor, protein kinase C (PKC), or myosin light chain kinase (MLCK), PGF2α-mediated increase in ANP secretion and positive inotropy were attenuated. Inhibitor for COX-1 or COX-2 did not cause any significant effects on atrial parameters. In hypertrophied rat atria, PGF2α-induced positive inotropy and ANP secretion were markedly attenuated whereas COX-2 inhibitor stimulated ANP secretion. The expression of COX-2 increased and the expression of PGF2α receptor mRNA decreased in hypertrophied rat atria. These results suggest that PGF2α increased the ANP secretion and positive inotropy through PLC–IP3–PKC–MLCK pathway, and the modulation of ANP secretion by COX-2 inhibitor and PGF2α may partly relate to the development of renal hypertension.