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

Abstract

-Peripubertal gilts (n = 25) were treated with corn oil (CO) or ovarian steroids, one month following an ovariectomy. The first day of treatment was assigned as the first day of the experiment. The gilts received: Group (Gr) I (n = 4) -CO (2 mL·day -1 from 1st to 12th day), Gr II (n = 4) and Gr III (n = 4) -progesterone (P 4 ; 10 to 100 mg·day -1 from 1st to 12th day), Gr IV (n = 5) -estradiol benzoate (EB; 400 mg·day -1 from 1st to 3rd day), Gr V (n = 4) and Gr VI (n = 4) -EB + P 4 (EB 400 mg·day -1 from 1st to 3rd day, 20 mg·day -1 at 6th and 9th day, 50 mg at 12th day plus P 4 10 to 100 mg from 4th to 15th day). All gilts were injected with oxytocin (OT; 20 IU; i.v.) on the following days of the experiment: 13th (Gr I and Gr II), 15th (Gr III and Gr IV), 16th (Gr V) and 18th (Gr VI). Concentrations of the PGF 2a metabolite -PGFM were determined in blood samples, collected from 30 min before to 120 min after OT injection. Baseline PGFM concentrations (30 min before OT) differed among treatment groups and were the highest in Gr V and Gr VI (P < 0.01 vs. other groups). The magnitude of the PGFM response to OT increased only in four of the five gilts of Gr IV and in three of the four gilts of Gr VI, and it was higher (P = 0.009) in Gr VI than in Gr IV. In the remaining groups, PGFM concentrations did not increase above the baseline in response to OT. The day after OT injection, oxytocin receptors (OTR) were found in the uterine tissues of all animals studied. The lowest OTR concentrations were in Gr I -75.5 ± 11.2 fmol·mg protein -1 and the highest in Gr IV -712.9 ± 86.7 fmol·mg protein -1 ; (P < 0.05 vs. other groups). The values of K d of OTR differed among groups (P < 0.001) and ranged from 1.62 ± 0.44 nM in Gr I to 12. 08 ± 1.9 nM in Gr VI. A positive correlation (r = 0.54; P < 0.01) between plasma E 2 and uterine OTR concentrations was observed. In conclusion, E 2 and P 4 are involved in both PGF 2a synthesis/secretion and OTR formation, however, full PGF 2a response to OT does not develop before puberty. Estrogens are evident stimulators of uterine OTR synthesis in gilts.prostaglandin F 2a secretion / oxytocin receptors / gilts Reprod. Nutr. Dev. 42 (2002) 327-338 327

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

“…Progesterone (P4) inhibits OTstimulated production of endometrial and myometrial PG via mechanisms including regulation of OTR expression, inositol phosphate accumulation and intracellular Ca 2+ response [7,19,26,27]. However, local factors affecting the response of the porcine uterus to OT during early pregnancy are unknown.…”

The Role of Oestradiol in the Uterine Peristalsis in the Perfused Swine Uterus

“…2003, 2004). Franczak et al. (2002) also stated that estrogens are evident stimulators of uterine oxytocin receptors synthesis in gilts.…”

“…Richter et al (2003) reported that oxytocin receptor expression is upregulated by oestrogens not only in pregnant but also in nonpregnant human uteri (Richter et al 2003(Richter et al , 2004. Franczak et al (2002) also stated that estrogens are evident stimulators of uterine oxytocin receptors synthesis in gilts. Also an increase in intrauterine pressure in response to oxytocin was most evident in sows in estrous (Zerobin and Spo¨rri 1972;Langendijk et al 2002a) and parturition (Zerobin and Spo¨rri 1972).…”

The effect of progesterone on oxytocin-stimulated intracellular Ca2+ mobilisation and prostaglandin secretion in porcine endometrium

“…Oxytocin regulates prostaglandin F2α (PGF2α) and prostaglandin E2 (PGE2) secretion from porcine endometrium during luteolysis and early pregnancy (Whiteaker et al 1995, Uzumcu et al 2000, Blitek and the estrous cycle and the period of pregnancy (Okano et al 1996, Franczak et al 2002.…”