This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Carnahan, K. G. Articles by Mirando, M. A. Search for Related Content PubMed Articles by Carnahan, K. G. Articles by Mirando, M. A.

Effect of oxytocin on concentration of PGF₂ in the uterine lumen and subsequent endometrial responsiveness to oxytocin in pigs

The aim of this study was to determine the effect of oxytocin on PGF₂ secretion into the uterine lumen of pigs and subsequent endometrial responsiveness to oxytocin in vitro. Cyclic, pregnant and oestradiol-induced pseudopregnant gilts were injected i.v. with vehicle or 20 iu oxytocin 10 min before hysterectomy on day 16 after oestrus. Concentrations of PGF₂ and 13,14-dihydro-15-keto PGF₂ (PGFM) were significantly increased in uterine flushings collected at hysterectomy (P < 0.05) in pregnant oxytocin-injected gilts. Concentrations of PGF₂ and PGFM were greater (P < 0.001) in pregnant than in pseudopregnant and cyclic gilts, and greater (P < 0.01) in pseudopregnant than in cyclic gilts. The ratio of PGFM:PGF₂ tended to be greater in cyclic (P < 0.06) and pseudopregnant gilts (P < 0.1) than in pregnant gilts. At 85 ± 5 min after oxytocin injection, endometrium from each gilt was incubated for 3 h for determination of phosphoinositide hydrolysis and PGF₂ secretion in response to treatment with 0 or 100 nmol oxytocin l^–1. Endometrial phosphoinositide hydrolysis in response to 100 nmol oxytocin l^–1 in vitro was greater (P < 0.05) in cyclic oxytocin-injected gilts than in cyclic vehicle-injected gilts. Treatment with oxytocin in vitro did not stimulate phosphoinositide hydrolysis significantly in vehicle- or oxytocin-injected pregnant gilts or pseudopregnant gilts. Endometrial PGF₂ secretion increased after treatment with 100 nmol oxytocin l^–1 in vitro in cyclic vehicle-injected (P < 0.01), cyclic oxytocin-injected (P < 0.01), pregnant vehicle-injected (P = 0.06), pseudopregnant vehicle-injected (P < 0.05) and pseudopregnant oxytocin-injected (P < 0.05) gilts, but not in pregnant oxytocin-injected gilts. The increase in PGF₂ in pseudopregnant oxytocin-injected gilts was less (P < 0.05) than that in cyclic oxytocin-injected gilts. These results indicate that oxytocin increases the concentration of PGF₂ and PGFM in the uterine lumen during pregnancy and may upregulate endometrial responsiveness to oxytocin during late dioestrus in pigs, but does not have the latter effect during early pregnancy or oestradiol-induced pseudopregnancy.