Changes in Uterine Secretion of Prostaglandin F2α in Response to Oxytocin during the Estrous Cycle, Early Pregnancy, and Estrogen-lnduced Pseudopregnancy in Swine1

Abstract

Thirty-one sows were used in an experiment designed to determine whether the ability of the porcine uterus to release prostaglandin (PG) F2 alpha in response to oxytocin was suppressed in pregnancy and pseudopregnancy. Sows were assigned to one of three treatment groups: nonbred (nonpregnant) controls (n = 8), pseudopregnant (5 mg estradiol benzoate, i.m., daily on Days 11-15 postestrus; n = 8), or bred (bred once daily throughout the estrous period; n = 15). Jugular venous blood samples were collected daily for quantification of progesterone. Pregnancy was determined by uterine examination at slaughter 51-72 days postmating. On the basis of progesterone and embryo recovery, bred sows were classified into three subgroups: confirmed pregnant (n = 4), suspected pregnant based on delayed luteal regression (n = 5), or bred/not pregnant (n = 6). All sows received an injection of oxytocin (30 IU, i.v.) on Days 12, 15, and 18 postestrus. Jugular venous blood samples were collected from 60 min prior to through 120 min after injection of oxytocin for quantification of 13, 14-dihydro-15-keto-PGF2 alpha (PGFM). Magnitude of response above baseline and area under the PGFM response curve (AUC) were calculated for each sow on each day and compared among treatment groups by analysis of variance. Responses in pregnant and suspected-pregnant sows were not different on any day examined; therefore the two groups were combined (n = 9) and considered pregnant for all subsequent analyses. Responses in the nonpregnant and bred/not pregnant sows were pooled and compared to the responses in the pregnant and pseudopregnant sows. Magnitudes of response were similar between these pooled groups on Day 12 (p > 0.5), but were less in pregnant and pseudopregnant sows on Days 15 and 18 (p < 0.01). When nonpregnant and bred/not pregnant sows were compared to each other, the magnitudes of the response were similar on Days 12, 15, and 18 (p > 0.3 on each day). In contrast, when pregnant and pseudopregnant sows were compared, pseudopregnant sows had a lower magnitude of response that was consistent across all 3 days (p < 0.02). Similar relationships were apparent for the AUC. These results demonstrate that uterine secretory responsiveness to oxytocin is suppressed during early pregnancy and that this effect may be mediated through estrogen secreted by conceptuses.

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.…”

Local and Systemic Effects of Embryos on Uterine Tissues During Early Pregnancy in Pigs

“…Oxytocin, acting through oxytocin receptors (OTR) in the endometrium and myometrium, is involved in the control of prostaglandin F2α (PGF2α) and prostaglandin E2 (PGE2) secretion in pigs [3][4][5][6][7][8]. Prostaglandin F2α is responsible for luteal regression in non-pregnant pigs [1,9], while prostaglandin E2 acts as a luteotrophic and antiluteolytic factor that promotes maintenance of the corpus luteum during early pregnancy in pigs [10,11].Alteration of PG secretion by OT is implicated in maternal recognition of pregnancy in pigs [12][13][14]. Moreover, OT stimulates myometrial secretion of PGF2α and PGE2 as well as the contractile activity of the porcine myometrium during early pregnancy [8,15,16].…”

“…Alteration of PG secretion by OT is implicated in maternal recognition of pregnancy in pigs [12][13][14]. Moreover, OT stimulates myometrial secretion of PGF2α and PGE2 as well as the contractile activity of the porcine myometrium during early pregnancy [8,15,16].…”

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.…”

“…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.…”