Changes in peripheral concentrations of 13,14-dihydro-15-keto-prostaglandin F2α induced by progesterone in swine1

Abstract

This experiment was designed to examine the effects of progesterone on endogenous and oxytocin-induced secretion of prostaglandin F2 alpha (PGF2 alpha) in sows. Peripheral concentrations of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) were used as an indirect measure of uterine PGF2 alpha secretion. Eight sows received twice daily injections of progesterone (160 mg/injection) on d 1 to 5 after estrus. Another eight sows received comparable injections of a corn oil injection vehicle. Each sow then received i.v. injections of oxytocin (30 IU) on d 10, 12, and 15 after estrus. Concentrations of PGFM were determined in jugular venous blood samples collected at -60, -45, -30, -15, 0, 2, 5, 10, 15, 30, 45, 60, 90, and 120 min after each oxytocin injection. The mean concentrations of PGFM in samples collected before injection of oxytocin (baseline), the magnitude of the PGFM response to oxytocin, and the area under the PGFM response curve (AUC) were calculated for the three oxytocin challenges administered to each sow. Baseline, magnitude, and AUC were low on d 10 after estrus and similar for the two treatment groups. On d 12 baseline, magnitude, and AUC remained low in the control sows; however, all three response variables increased in sows that received progesterone. By d 15, all three variables were high and similar in both treatment groups. In conclusion, progesterone, administered early in the estrous cycle, seems to promote premature secretion of PGF2 alpha as indicated by the high basal concentrations of PGFM observed before injection of oxytocin on d 12.(ABSTRACT TRUNCATED AT 250 WORDS)

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

“…At estrus (Day 0), each sow was assigned randomly to one of three treatment groups: 1) nonpregnant controls (n = 8), 2) pseudopregnant (5 mg estradiol benzoate, i.m., daily on Days 11-15 postestrus; n = 8), or 3) bred (bred once daily throughout estrus; n = 15). On the morning of Day 1, the jugular vein was cannulated as described previously [24]. Jugular venous blood samples (10 ml) were collected daily beginning on Day 1 until the following estrus or through Day 25 if estrus was not observed.…”

“…Concentrations of progesterone in serum samples collected daily throughout the estrous cycle were quantified with a commercial, solid-phase RIA kit (Coat-a-Count; Diagnostic Products, Los Angeles, CA) as described previously [24]. Samples were evaluated in four assays.…”

“…Recently, oxytocin has been shown to be a stimulus for PGF 2 . secretion in the sow [10,[23][24][25][26]. Endogenous oxytocin may contribute to the regulation of PGF 2 secretion during luteolysis.…”

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].…”