Changes in Uterine Secretion of Prostaglandin F2α and Luteal Secretion of Progesterone in Response to Oxytocin during the Porcine Estrous Cycle1

Abstract

The purpose of this experiment was to determine whether the ability of oxytocin to stimulate uterine secretion of prostaglandin F2 alpha (PGF2 alpha) and luteal secretion of progesterone changes during the porcine estrous cycle. Nineteen multiparous sows were observed for estrus. After one estrous cycle of normal length, sows were assigned randomly to receive an injection of oxytocin (30 IU, i.v.) in the EARLY (Days 4-6; n = 6), MID (Days 9-11; n = 7), or LATE (Day 15; n = 6) stage of the estrous cycle. Concentrations of 13, 14-dihydro-15-keto-PGF2 alpha (PGFM) and progesterone were determined in jugular venous serum samples collected at -60, -45, -30, -15, 0, 2, 5, 10, 15, 30, 45, 60, 90, and 120 min after injection of oxytocin. The magnitudes of the PGFM and progesterone responses and the area under the respective response curves (AUC) were calculated for each sow. Concentrations of PGFM did not change in response to oxytocin administered during the EARLY or MID portions of the estrous cycle. Concentrations increased rapidly in 4 of 6 sows that received oxytocin LATE in the estrous cycle. Both magnitude and AUC were greater LATE in the estrous cycle than at either EARLY or MID cycle (p less than 0.05). Thus, uterine secretory responsiveness to oxytocin develops between Days 11 and 15 postestrus in the sow. For progesterone, a transient increase was observed immediately following injection of oxytocin at MID cycle (p less than 0.05), but not at the other times examined. Therefore, oxytocin appears to be capable of stimulating secretion of progesterone from the functionally mature corpus luteum.

Oxytocin and tumor necrosis factor α stimulate expression of prostaglandin E2 synthase and secretion of prostaglandin E2 by luminal epithelial cells of the porcine endometrium during early pregnancy

“…In sheep, the major physiological stimulus for PGF 2a secretion is oxytocin (OXT; McCracken et al 1999). Similarly, numerous reports indicate that OXT stimulates PGF 2a secretion from the porcine endometrium during the late luteal phase in vivo (Kieborz et al 1991, Carnahan et al 1996, Edgerton et al 1996 and in vitro (Whiteaker et al 1994, Tysseling et al 1996, Blitek & Ziecik 2005.…”

The influence of estradiol and progesterone on the concentrations of uterine oxytocin receptors and plasma PGFM in response to oxytocin in ovariectomized gilts

“…Moreover, in our earlier study (Franczak, data unpublished) 20 IU OT were administered to cyclic gilts on days 15 to 18 of the oestrous cycle and resulted in a significant increase of plasma PGFM concentration. In this study plasma PGFM concentrations in OVX and steroidprimed gilts, were distinctly lower compared to the data of cyclic sows [10,20,36]. We ovariectomized peripubertal six to seven-month old gilts.…”

“…In cyclic gilts basic and OT-stimulated plasma PGFM concentrations were higher on days 14-16 of the oestrous cycle, i.e. on days when plasma P 4 started to decline [20,36].…”

“…Concentrations of specific OTR in the endometrium and PGF 2a respond to OT challenge change during the course of the oestrous cycle in gilts [10,20,33,51], ewes [43,48] and cows [13,31]. Generally, the highest OTR concentrations are observed during oestrus and the lowest in the mid-luteal phase.…”

“…However, in pigs, luteolysis is not preceded by a temporal increase in endometrial OTR [29,33]. In sows, the concentration of plasma PGF 2a metabolite (PGFM) significantly increased in response to the OT administered around luteolysis (days [14][15][16], but there is no response during the early luteal phase (days 4-6) and a weak response is found in the mid-luteal phase (days 9-12) of the oestrous cycle [6,20]. These data indirectly suggest that cyclic changes of estrogens (E 2 ) and the P 4 level during the oestrous cycle may influence uterine OTR concentration and PGF 2a response to OT.…”