Prostaglandin secretion by perifused porcine endometrium: further evidence for an endocrine versus exocrine secretion of prostaglandins.
ABSTRACT Bilateral perifusion devices were utilized for measurement of prostaglandin secretion by luminal and myometrial surfaces of porcine endometrium. Tissues were collected from Days 10, 12 and 14 pregnant, Day 14 cyclic and Day 14 estrogen-induced pseudopregnant gilts. Each tissue was placed into duplicate perifusion devices and perifused with Krebs-Ringer Bicarbonate solution at 3 ml/10 min for 2 h, fractions collected every 10 min and oxytocin (1 IU/ml) perifused during fractions 6-10 to the luminal side of one chamber and to the myometrial side of the other chamber. Secretion rates of PGF were higher (P less than 0.05) than PGE2 for each status. Secretion rates of PGF and PGE2 were higher (P less than 0.01) from the luminal side for Day 12 pregnant, Day 14 pregnant and Day 14 pseudo-pregnant gilts, whereas secretion was higher from the myometrial side for Day 10 pregnant and Day 14 cyclic gilts. Oxytocin increased (P less than 0.01) prostaglandin secretion from the luminal side regardless of reproductive status. Pregnancy at Day 12 and Day 14, as well as estrogen treatment, were associated with prostaglandin secretion in a luminal (exocrine) orientation versus a myometrial (endocrine) orientation for Day 14 cyclic and Day 10 pregnant gilts. These data indicate an estrogen associated switch between Days 10 and 12 of pregnancy from an endocrine to an exocrine secretion of prostaglandins.
Article: Up-regulation of oxytocin receptors in porcine endometrium by adenosine 3',5'-monophosphate.[show abstract] [hide abstract]
ABSTRACT: Porcine endometrial cells (a mixture of epithelial, stromal, and glandular cells) were examined for the presence of oxytocin (OT) receptors using a cell culture system and a 125I-labeled OT antagonist. Binding specificity was tested in displacement studies with various related peptides. Scatchard analyses revealed the presence of a binding site with a dissociation constant (Kd) = 0.9 nM and a capacity of 1.9 fmol/10(5) cells. These cells, which were obtained from prepubertal gilts and thus had not been exposed to endogenous ovarian steroids, were used as a model to evaluate the possible action of ovarian steroids and intracellular cAMP on OT receptors. Although ovarian steroids showed no effect on OT receptors, forskolin (an adenylate cyclase activator) and dibutyryl cAMP caused 1.5- to 1.6-fold increases in specific binding of OT without changing the binding affinity. When the endometrial cells were exposed to OT (0.1-1000 nM) in combination with arachidonic acid (10 microM), OT stimulated prostaglandin F2 alpha secretion in a dose-dependent manner. These results indicate the presence of functional OT receptors in prepubertal porcine endometrial cells and suggest that the concentration of OT receptors may be regulated by one or more substances that raise intracellular cAMP levels.Biology of Reproduction 11/1997; 57(4):723-8. · 4.01 Impact Factor
Journal of Mammalian Ova Research 01/2009;
Article: Exogenous oxytocin stimulates uterine secretion of prostaglandin F2 alpha in cyclic and early pregnant swine.[show abstract] [hide abstract]
ABSTRACT: Oxytocin (OT) stimulates endometrial secretion of prostaglandin (PG) F2 alpha around the time of corpus luteum regression in ruminants, but the stimulus for luteolytic PGF2 alpha release in cyclic pigs is not clear. We previously reported that OT stimulates endometrial phosphoinositide hydrolysis and PGF2 alpha release in vitro, and that exogenous OT administered on Days 10-16 caused a uterine-dependent reduction in interestrous interval. In this study, the development of endometrial responsiveness to OT in cyclic, early pregnant, and ovarian-intact hysterectomized gilts was investigated. On Day 7 (onset of estrus = Day 0), 26 gilts were fitted with indwelling jugular catheters, and 5 of these gilts were hysterectomized. Cyclic (n = 5), pregnant (n = 6), and ovarian-intact hysterectomized (n = 5) gilts received i.v. injections of 20 USP units OT (equivalent to 20 IU or 40 micrograms/ml) on Days 10, 12, 14, and 16; and cyclic controls (n = 5) and pregnant controls (n = 5) received i.v. injections of vehicle. Concentration of 13,14-dihydro-15-keto-PGF2 alpha (PGFM; the major stable metabolite of PGF2 alpha) was measured in jugular venous plasma collected at 10-min intervals, from 20 min before to 120 min after i.v. injections of OT or vehicle. Plasma progesterone was measured in blood samples collected daily from Day 9 through return to estrus (cyclic gilts) or through Day 30 (pregnant and hysterectomized gilts). Vehicle-treated and OT-treated cyclic gilts were not responsive to OT on Days 10 and 12, and had similar plasma PGFM profiles on these days. However, OT-treated cyclic gilts were responsive (p < 0.01) to OT on Days 14 and 16, and peak concentrations of PGFM were detected in jugular plasma 10 min after OT injection. Concentrations of PGFM did not increase after vehicle injection on any day in controls. Similarly, PGFM in ovarian-intact hysterectomized gilts did not increase on any day after OT injection, indicating that the uterus was probably the source of OT-induced PGFM in cyclic gilts. Pregnant vehicle-treated gilts also did not have increased PGFM on any day after injection of vehicle. Pregnant OT-treated gilts had increased (p < 0.01) PGFM concentrations after OT injection on all days that were higher than concentrations in cyclic gilts on Days 10 and 12, but lower than those in cyclic gilts on Days 14 and 16 (p < 0.01). The concentration of plasma progesterone in cyclic gilts did not decrease until Days 15-16 (p < 0.01). Plasma progesterone was maintained in pregnant and hysterectomized gilts and was not influenced by OT treatment. These results indicated that 1) endometrial responsiveness to OT in cyclic gilts developed between Days 12 and 14 postestrus, 2) endometrial responsiveness to OT developed before luteolysis was initiated, and 3) endometrial responsiveness to OT in pregnant pigs developed before Day 10 of pregnancy and was attenuated on Days 14 through 16. These results are consistent with the hypothesis that OT may promote pulsatile luteolytic secretion of PGF2 alpha during corpus luteum regression in swine and that responsiveness to OT was suppressed to maintain corpus luteum function during early pregnancy.Biology of Reproduction 11/1996; 55(4):838-43. · 4.01 Impact Factor