Calcium potentiates the effect of estradiol on PGF2α production in the bovine endometrium

Background： Estradiol （E2） is required for luteolysis in cows and its injection stimulates prostaglandin F2α （PGF2α） release. The main goal of our study was to investigate the ability of endometrial explants and cells treated with E2 and the calcium ionophore （CI） A23187 to synthesize PGF2α. Results： Treatment with E2 in vivo resulted in a 48.4% increase of PGF2α production by endometrial explants treated in vitro with A23187. Production of PGF20 was better stimulated with A23187 at concentrations of 10^-6 and 10^-5 mol/L compared with other concentrations used. The concentration of PGF2α for untreated bovine endometrial cell cultures was 33.1 pg/mL, while for cultures treated with E2, A23187, or a combination of E2 and A23187, the PGF2α concentration was 32.5, 92.4 and 145.6 pg/mL, respectively. Conclusions： Treatment with A23187 tended to stimulate PGF20 production. In the presence of E2, A23187 significantly stimulated PGF20 synthesis. It appears that A23187 potentiates the effects of E2 with respect to synthesis of endometrial PGF2α in cattle.

Exacerbated conceptus signaling does not favor establishment of pregnancy in beef cattle

Background: Insufficient production of anti-luteolytic signals by the pre-attachment embryo is considered a major cause of pregnancy failure in cattle.We tested the hypothesis that transfer of multiple blastocysts(n = 5/recipient) and progesterone(P4) supplementation amplify anti-luteolytic signaling and reduce embryonic losses in beef cattle.Cows detected in estrus(D0; n = 104) were assigned randomly to receive 150 mg of injectable long-acting P4(iP4) or vehicle(non-iP4) on D4 and transcervical transfer of none or five,grade 1,not-frozen,in vitro-produced blastocysts,on D7.Luteal development and time of structural luteolysis were monitored by ultrasonography.Plasma P4 concentrations were determined on D4,D5 and D7,and daily between D14 and D20.Conceptus signaling was monitored by transcript abundance of interferon-stimulated gene 15(ISG15) in peripheral blood mononuclear cells isolated on D14,D16,D18 and D20.Early embryonic mortality(EEM) was defined as the absence of ISG15 m RNA upregulation over time and/or luteal regression up to D20.Late embryonic mortality(LEM) was defined as the absence of a conceptus with a heartbeat on pregnancy diagnosis at D30(PD30) after observing upregulation of ISG15 mRNA and extension of luteal lifespan.Pregnant cows presented conceptuses with heartbeat at PD30.Results: On D5,iP4-treated cows had P4 concentrations 2.07-fold greater than non-iP4 treated(P < 0.001).On D7,P4 concentrations were similar.Pregnant and LEM animals showed a progressive increase in the abundance of ISG15 from D14 to D20.iP4-treated cows detected pregnant at PD30 had 1.53-fold greater abundance of ISG15 mRNA between D14 and D20 than non-iP4 treated cows(P = 0.05).iP4 doubled the frequency of EEM while it did not affect LEM.At PD30,embryonic survival was 37.0% vs.55.6% for iP4-treated vs.control cows.Majority of pregnant cows(71%)presented only a single viable embryo.Conclusions: A substantial proportion of cows had EEM(31%) and LEM(20%) even after transferring multiple blastocysts.This argues that mortality was due to poor uterine receptivity that could not be reversed by supplemental P4 or overcome by transferring multiple blastocysts.Further,a given uterine environment was not necessarily adequate to all embryos.

Identification and Possible Function of Tissue-type and Urokinase-type Plasminogen Activators and Plasminogen Activator Inhibitor in Corpus Luteum of Rhesus Monkey

Two types of plasminogen activators, tissue type (tPA) and urokinase type(uPA),and a plasminogen activator inhibitor (PAI-1) have been identified in ovariangranulosa cells (GC) of both rat and rhesus monkey. Interaction and coordinated expression of tPA and PAI-1 in the same tissue cells are closely related with certain reproductive processes such as ovulation, spermatogenesis and endometrium cycle. In our previous studies on gonadotropin-induced ovulation in rhesus monkeys,we

Role of plasminogen activators and inhibitors in reproduction

The recent progress in the studies on the role of local and directed fibrinolysis controlled by plasminogen activators (PAs) and regulated by their inhibitors (PAIs) in reproduction is summarized. Hormone-induced coordinated expression of tissue type PA (tPA) and PAI type-1 (PAI-1) in the ovary is involved in the processes of ovulation and luteal regression; increases in urokinase type PA (uPA) and PAI-1 activity in the early stage of luteinized follicles may be responsible for ovarian tissue remodeling and angiogenesis; the PA system has been found to play an important role in spermatogenesis in testis and modulation of sperm maturation in epididymis. PA and matrix matalloproteanase (MMP) and their respective inhibitors have also been identified in trophoblast and uterus. The targeted proteolytic activity generated by the two systems may play an essential role in the processes of the cyclic uterine angiogenesis, implantation and pla-centation as well as parturition.