Immunopresence and functional activity of prostaglandin-endoperoxide synthases and nitric oxide synthases in bovine corpora lutea during diestrus

The aim of this study was to evaluate the occurrence and the activity of prostaglandin-endoperoxide synthase 1 (PTGS1), PTGS2, and endothelial, neuronal, and inducible nitric oxide synthase (e-, n-, and iNOS) in early, mid, late, and regressive corpora lutea (CL) of bovines during diestrus. PTGS1 immunoreactivitywas localised mainly in the cytoplasm of small luteal cells, whereas PTGS2 was detected in the cytoplasm of large luteal cells during early, mid, and late stages. The immunoexpression of all NOS isoforms was observed in the nuclei of luteal cells in the CL stages examined. PTGS1 enzyme activity was higher in late CL and lower in regressive ones; PTGS2 increased from early to late CL andlowered in regressive ones. Constitutive NOS enzymatic activity (eNOS plus nNOS) was higher in late CL and lower in regressive ones; iNOS was lower in regressive CL. These results support the idea that PTGSs and NOSs regulate the bovine CL life span mainly during the transition from the luteotrophic to the luteolytic phase

The physiological dilemma of the high progesterone syndrome in rabbit does

This work focused on the mechanisms that may cause multiple asynchronous ovulations and alter normal ovarian function in order to characterize the high progesterone (P+) syndrome in rabbit does, that, having abnormally high plasma progesterone concentration at the time of insemination, fail to become pregnant. At different luteal stages, at either days 4, 9, or 13 of pseudopregnancy, induced by GnRH injection (d-0), two groups of rabbits (n=5/group) were treated with saline or 0.8 \ub5g GnRH. Blood samples were collected from d-0 to d-26 of pseudopregnancy. At d-4, GnRH injection prolonged (P<0.05) the functional CL life span by 3 to 4 d over that of controls. At d-9, GnRH caused a transient decline (P<0.01) of progesterone for the following 3 d but, thereafter, increased again and remained higher (P<0.01) than controls up to d-26. At d-13, progesterone fell to 1 ng/ml within one day following GnRH, but then gradually increased. Based of these progesterone profiles, it can be argued that, at both mid- and late-luteal phase, GnRH triggered luteolysis and induced ovulation followed by the formation of a new generation of CL. For the in vitro study, CL, collected at days 4, 9, and 13 of pseudopregnancy, were incubated with GnRH, GnRH-antagonist, PLA2 inhibitor, and PLC inhibitor. GnRH decreased (P<0.01) progesterone secretion by d-9 and d-13 CL cultured in vitro; by converse, GnRH antagonist, increased (P<0.01) progesterone release from d-4 CL. Co-incubation of GnRH with GnRH antagonist increased (P<0.01) progesterone release in d-4 CL, but had an opposite effect (P<0.01) on d-9 and d-13 CL. PLC inhibitor reversed the GnRH effects in both d-9 and d-13 CL, while PLA2 inhibitor did not change progesterone release. These data suggest that rabbit CL express a functional receptor for GnRH, likely of type II, that utilizes the PLC post transductional cascade. Luteal FSH-R and LH-R mRNA relative abundances did not differ between d-4 and d-9 CL, but were two- to three-fold (P 640.01) higher, respectively, at d-13. StAR mRNA was highly expressed at d-4 of pseudopregnancy, but then markedly declined (P 640.01) at d-9 and d-13. Taken together, our results show that GnRH triggers i) functional regression when CL acquire luteolytic capacity from d 9 of pseudopregnancy onward, and ii) multiple asynchronous ovulations, thus partly explaining the P+ syndrome associated with the simultaneous coexistence of two population of \u201cfresh\u201d and \u201cold\u201d CL, although not yet the underlying causes

Regolazione della funzione e regressione luteale nel coniglio

La funzione principale del corpo luteo (CL) \ue8 la produzione del progesterone determinante per conseguire e portare a termine la gravidanza. Nel coniglio, i meccanismi che controllano lo sviluppo dei CL, la funzione secretoria e la regressione coinvolgono diversi fattori intra- ed extra-ovarici con azione luteotropa e luteolitica tra cui gli estrogeni e la prostaglandina F2 (PGF2 ). La loro azione risultante \ue8 tuttavia mediata da una complessa serie di interazioni che coinvolgono meccanismi in cui un ruolo non trascurabile \ue8 svolto da fattori ad azione autocrina e/o paracrina, emersi nel corso degli anni, quali principali regolatori dell\u2019attivit\ue0 luteale, tra i quali: citochine (es. interleuchine, leptina), peptidi vasoattivi (es. ossido nitrico, endotelina) e fattori legati all\u2019apoptosi (es. membri della famiglia BCL2 e TP53). Il CL neoformato sembra essere resistente all\u2019azione della PGF2 . La competenza luteolitica all\u2019azione della PGF2 aumenta progressivamente con lo sviluppo del CL e viene pienamente acquisita dal 9\ub0 giorno di pseudogravidanza. I risultati riassunti in questo lavoro con differenti approcci metodologici, testimoniano che, anche nei CL apparentemente refrattari all\u2019azione della PGF2 , esiste una intensa attivit\ue0 molecolare determinata da questa luteolisina. I dati ottenuti approfondiscono meccanismi biologici che sono di estremo interesse nel campo della fisiologia ovarica ma che stanno alla base anche della patologia riproduttiva.The main function of corpus luteum (CL) is the production of progesterone which is necessary for achieving and maintaining a successful pregnancy. In rabbits, the mechanisms controlling luteal development and secretory function as well as luteal regression involve different intra- and extra-ovarian factors with luteotrophic and luteolytic actions, including estrogens and prostaglandin F2 (PGF2 ). These factors act by complex interactions involving autocrine and/or paracrine mechanisms. Over the past few years, they emerged as important regulators of luteal activity: cytokines (e.g. interleukins, leptin), vasoactive peptide (e.g. endothelin, nitric oxide) and apoptotic factors (e.g. BCL2 family members and TP53). The newly formed CL appear to resist the luteolytic action of PGF2 . The acquisition of luteal competency to PGF2 increases progressively with the CL development and, at day 9 of pseudopregnancy, they are fully responsive. The results here summarized show that in CL apparently resistant to the luteolytic action of PGF2 exists an intense molecular activity induced by this luteolysine. The data obtained with different methodological approaches provide further details on biological mechanisms that are relevant in the field of ovarian physiology, as well as in that of reproductive pathology

Expression patterns of cytokines, p53 and nitric oxide synthase enzymes in corpora lutea of pseudopregnant rabbits during spontaneous luteolysis

The gene expressions for macrophage chemoattractant protein-1 (MCP-1), interleukin (IL)-1 beta, IL-2 and p53 were examined by semi-quantitative RT-PCR in corpora lutea (CL) of rabbits during spontaneous luteolysis at days 13, 15, 18 and 22 of pseudopregnancy. In the same luteal tissue, total activity of nitric oxide (NO) synthase (NOS) and genes for both endothelial (eNOS) and inducible (iNOS) isoforms were also analysed. From day 13 to 15, MCP-1 and IL-1 beta mRNA levels rose (P < or = 0.01) almost 2-fold, and the transcript for p53 almost 8-fold, but then all dropped (P < or = 0.05) from day 18 onward. IL-2 mRNA abundance was higher (P < or = 0.01) on day 13 and then gradually declined. During luteolysis, eNOS mRNA decreased 40% (P < or = 0.05) by day 15, but thereafter remained unchanged, while iNOS mRNA was barely detectable and did not show any clear age-related pattern throughout the late luteal stages. Total NOS activity progressively increased (P < or = 0.01) from day 13 to 18 of pseudopregnancy and then dropped to the lowest (P < or = 0.01) levels on day 22. Luteal progesterone content also declined during CL regression from 411 to 17 pg/mg found on days 13 and 22 respectively, in parallel with the decrease in blood progesterone concentrations. These data further support a physiological role of NO as modulator of luteal demise in rabbits. Locally, luteal cytokines may be involved in the up-regulation of NOS activity, while downstream NO may inhibit steroroidogenesis and induce expression of p53 gene after removal of the protective action of progesterone

Vasoactive peptides in the luteolytic process activated by PGF2alpha in pseudopregnant rabbits at different luteal stages

To study the role of endothelial factors in luteal function, the dynamic profiles of genes for endothelin 1 (EDN1), its receptor subtypes, EDNRA and EDNRB, and angiotensin converting enzyme (ACE) were examined in corpora lutea (CL) obtained from rabbits on Days 4 and 9 of pseudopregnancy after prostaglandin (PG) 172a analogue (alfaprostol) treatment. The cell type distribution of EDN1 in the ovaries and its mechanisms of actions in vitro and in vivo were also studied. Positive immunostaining for EDN1 was localized in the luteal and endothelial cells, in granulosa cells of the follicles, and in the ovarian epithelium. The basal mRNA levels for EDNRA, EDNRB, and ACE were lower (P <= 0.01) in Day-4 CL than in Day-9 CL, whereas those for EDNi did not differ between these two time-points. On Day 4, the luteal EDN1, EDNRA, EDNRB, and ACE mRNA levels were similarly increased two-fold (P <= 0.01) 1.5 h after alfaprostol injection, and did not show further changes in the subsequent 24 h. On Day 9, alfaprostol challenge transiently up-regulated (P < 0.01) the luteal ACE transcripts at 1.5 h, and those of EDN1 at 1.5 h and 3 h, whereas the EDNRA and EDNR8 transcript levels remained unchanged during the course of luteal regression. EDN1 decreased (P < 0.01) progesterone release and increased (P <= 0.01) PGF2 alpha secretion and NOS activity via the PLC/PKC pathway in Day-9 CL, but not in Day-4 CL, cultured in vitro. EDN1-induced, but not alfaprostol-induced luteolysis, was blocked by cotreatment in vivo with the ACE antagonist captopril. These findings support the hypothesis that PGF2 alpha regulates luteolysis through intraluteal activation of the reninangiotensin/EDN1 systems in CL that have acquired luteolytic competence

Aglepristone (RU534) administration to non-pregnant bitches in the mid-luteal phase induces early luteal regression

The effect of the antiprogestagen aglepristone (10 mg/kg bw), administered at days 29 and 30 following the estimated day of LH surge (day 0), on corpora lutea (CL) function was examined during the diestrus phase of non-pregnant bitches. Aglepristone shortened (P < 0.01) the luteal phase and complete luteolysis (progesterone <2 ng/mL) was observed at days 40.8 ± 3.5 and 71.5 ± 4.6 (means ± SD; n = 9/group) in treated and control bitches, respectively. Peripheral estradiol-17β concentrations declined from 91.5 ± 14.3 pg/mL at day 9 to 50 pg/mL at day 18, remaining at approximately the same levels thereafter in both treated and control bitches. Intraluteal in vitro synthesis of progesterone and estradiol-17β released by CL explanted at day 38 from control bitches (511.9 ± 285.6 and 40.7 ± 17.2 pg/mg protein, respectively) did not differ from that of treated. From day 38, intraovarian hemodynamic variables (arterial blood flow, systolic peak, and end-diastolic velocities), monitored by color-coded and pulsed Doppler, decreased more steeply (P < 0.01) in aglepristone-treated (n = 4) than in control (n = 4) bitches, whereas the resistance index increased (P < 0.01) in treated animals. All the blood flow parameters were undetectable at 60 ± 3.6 and 68 ± 2.0 days (medians ± SD) after LH peak in treated and control bitches, respectively. In conclusion, aglepristone administration to dogs during the mid-luteal phase markedly accelerates the luteolytic process which is accompanied by a parallel decline in ovarian blood flow supply with a shift from approximately 8 to 10 days

Food restriction during pregnancy in rabbits: effects on hormones and metabolites involved in energy homeostasis and metabolic programming

This study examined the effects of food restriction during rabbit pregnancy on hormones and metabolites involved in energy homeostasis and metabolic programming. Pregnant does were assigned to four groups: the control group was fed a standard ration while the others received a restricted amount of food (30% restriction) during early (0-9 days), mid (9-18 days), and late (19-28 days) pregnancy. The pregnancy induced a coordinated range of adaptations to fulfil energy requirements of both mother and foetus, such as hyperleptinaemia and hyperinsulinaemia, reduced insulin sensitivity, increased cortisol and non-esterified fatty acid. Food restriction altered leptin, insulin, T3, non-esterified fatty acids and glucose concentrations depending on the gestational phase in which it was applied. Collectively, present data confirm that the endocrinology of pregnancy and the adaptive responses to energy deficit make the rabbit an ideal model for studying nutritional-related disorders and foetal programming of metabolic disease. (C) 2014 Elsevier Ltd. All rights reserved

Leptin receptor expression and in vitro leptin actions on prostaglandin release and nitric oxide synthase activity in the rabbit oviduct

In this study, we have examined the presence and the distribution of receptors for leptin (Ob-R) in the oviduct of rabbits, and the effects of leptin on the release of prostaglandin (PG) F2alpha and PGE2 and on the activity of nitric oxide (NO) synthase (NOS) by oviducts cultured in vitro. Rabbits were killed during the follicular phase and the oviducts were incubated in vitro with leptin, PGF2alpha, PGE2, NO donor and inhibitors of NOS and cyclo-oxigenase (COX). Using immunohistochemistry, Ob-R-like positive reaction was observed only in the cytoplasm of secretory cells, having stronger intensity in the infundibulum and ampulla tracts than in the isthmus. Both leptin and NO donor inhibited PGE2 release, whereas they enhanced PGF2alpha release; NOS inhibitor alone or with leptin increased PGE2 and decreased PGF2alpha production; NOS activity was enhanced by leptin, while PGs did not affect this enzyme. This study suggests that the oviduct could be a potential target for endocrine regulation by leptin, whose circulating levels may act as a metabolic signal modulating oviductal PG release through mediation of the NOS/NO system