Free Access
Reprod. Nutr. Dev.
Volume 42, Number 4, July-August 2002
Page(s) 327 - 338
Reprod. Nutr. Dev. 42 (2002) 327-338
DOI: 10.1051/rnd:2002029

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

Anita Franczaka, Jaroslaw Staszkiewicza, Marek Koziorowskib and Genowefa Kotwicaa

a  Department of Animal Physiology, University of Warmia and Mazury, Olsztyn, Oczapowski st. 5, 10-178 Olsztyn, Poland
b  Department of Animal Physiology and Reproduction, University of Rzeszów, Rzeszów, Poland

(Received 11 March 2002; accepted 24 June 2002)

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 $\cdot$day -1 from 1st to 12th day), Gr II ( n = 4) and Gr III ( n = 4) - progesterone (P 4; 10 to 100 mg $\cdot$day -1 from 1st to 12th day), Gr IV ( n = 5) - estradiol benzoate (EB; 400 $\mu$g $\cdot$day -1 from 1st to 3rd day), Gr V ( n = 4) and Gr VI ( n = 4) - EB + P 4 (EB 400 $\mu$g $\cdot$day -1 from 1st to 3rd day, 20 $\mu$g $\cdot$day -1 at 6th and 9th day, 50 $\mu$g 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 $_{2\alpha}$ 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 $\pm$ 11.2 fmol $\cdot$mg protein -1 and the highest in Gr IV - 712.9 $\pm$ 86.7 fmol $\cdot$mg protein -1; ( P < 0.05 vs. other groups). The values of K $_{\rm d}$ of OTR differed among groups ( P < 0.001) and ranged from 1.62 $\pm$ 0.44 nM in Gr I to 12. 08 $\pm$ 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 $_{2\alpha}$ synthesis/secretion and OTR formation, however, full PGF $_{2\alpha}$ response to OT does not develop before puberty. Estrogens are evident stimulators of uterine OTR synthesis in gilts.

Key words: prostaglandin F $_{2\alpha}$ secretion / oxytocin receptors / gilts

Correspondence and reprints: Genowefa Kotwica

© INRA, EDP Sciences 2002