Relationship between Peripartal Plasma Oxytocin and Prostaglandin F2.ALPHA. Metabolite and Placental Expulsion Time in Heavy Draft Mares

Abstract

Abstract. The aim of this study was to clarify the relationship between circulating oxytocin (OT) and PGF2α metabolite (PGFM) in mares at the third stage of labor and placental expulsion time in order to investigate a cause of retained placenta of which the incidence increase in a heavy draft mare. Blood was sampled every 5 min from foaling to expulsion of the placenta in 18 heavy draft mares to evaluate circulating OT and PGFM. The relationships between OT and PGFM concentration and recorded placental expulsion times were investigated. The results were as follows (1) The highest level of OT concentration was observed close to foaling in 15 mares. (2) The OT concentrations close to foaling were variable with a large difference from the lowest concentration, 22.1 pg/ml, to the highest concentration, 209.3 pg/ ml. (3) The highest level of PGFM was observed close to foaling in 17 mares. (4) During the 60 min following foaling, the OT concentrations of the mares (n=11) that had a shorter placental expulsion time (i.e., <1 h), were significantly higher than those of the mares (n=7) that had a longer placental expulsion time (i.e., >1 h; P<0.05). Collectively, the OT concentration immediately after foaling is negatively related to the placental expulsion time. Deficiency of OT secretion at foaling have should be considered as one of the causes of retained placenta in heavy draft mares. Key words: Heavy draft mare, Oxytocin, 15-keto-dihydro prostaglandin F2α (PGFM), Placental expulsion (J. Reprod. Dev. 54: [270][271][272][273][274] 2008) ecently, the heavy draft horses of Japan have increased in size and become one of the largest breeds in the world. Retained placenta is occurring more frequently in heavy draft mares due to corpulence with lack of exercise because they are not used for work. A prolonged retained placenta in a mare causes a puerperal infectious disease and laminitis, and it may also cause death. Several causes of retained placenta, such as uterine inertia, placentitis, chill stress and hormone imbalance, have been considered [10,17,20]. Extension of the placental expulsion time reduces the subsequent conception rate in mares [9]. Although the conception rate of foaling heat in mares whose placental expulsion time was less than 1 hour was 66%, the conception rate of mares in which the placental expulsion time exceeded 4 h fell to 51.7% [9]. Manual removal of the placenta led to a decrease in subsequent fertility [9]. The level of circulating oxytocin (OT) rises rapidly in the 2nd stage of delivery in mares [1,8, 24]. Moreover, it is known that OT secretion helps discharge milk from the mammary glands [5,21]. Prostaglandin F2α (PG) might play a role in contraction of the myometrium at delivery. The circulating PG concentration in mares is determined generally by measurement of 15-keto-dihydro PGF2α (PGFM) [2,8,16]. The PGFM concentration, which is PG and its metabolic product, rises during the last stage of pregnancy or at the time of delivery [2,8,16,18,20,21]. According to detailed observations throu...

Relationship between the Placental Retention Time and the Reproductive Performance at the Foal Heat in Thoroughbred and a Comparison with Heavy Draft

“…Although RP has been variously suggested to be caused by dystocia [16], infection [12], edema of placenta [4], uterine inertia due to hormonal imbalance, e.g. oxytocin or prostaglandin F 2α [6, 7, 16], and vitamin E and selenium deficiency [8], the process that leads to RP is still unclear. The postpartum time interval for definition of RP varies from author to author, and has been reported as 30 min [12], 1 hr [9, 16] 2 hr [15], 3 hr [1, 3, 10, 13, 14] and 6 to 12 hr [18].…”

Prostaglandins and the regulation of parturition in mares

“…1995). Low oxytocin concentrations also have been reported in mares with delayed placental delivery (Ishii et al . 2008; F.E.…”

“…In other species, reduced maternal prostaglandin concentrations at birth are associated with retained fetal membranes (Olson 2003). This relationship was not observed in one study of heavy draught mares (Ishii et al 2008) but, when prostaglandins were blocked by administration of the PGHS-2 inhibitor, flunixin meglumine, prior to labour, placental delivery was delayed (Vivrette et al 1995). Low oxytocin concentrations also have been reported in mares with delayed placental delivery (Ishii et al 2008;F.E.…”

Dynamic Changes in the Myometrium during the Third Stage of Labor, Evaluated Using Two-Dimensional Ultrasound, in Women with Normal and Abnormal Third Stage of Labor and in Women with Obstetric Complications

“…These differences can be a representation of a contractile phenomenon in the upper segment (40-42), and a relaxatory process in the lower uterine segment (33) probably influenced by the existing hormonal milieu (local and serum concentration of estrogen, progesterone, oxytocin, prostaglandin, corticotropin), as well as the delicate balance on their receptors among uterine segments (27-30, 33, 44-47). …”