Oxytocin stimulates secretion of prostaglandin F(2alpha) from endometrial cells of swine in the presence of progesterone

Oxytocin (OT) stimulates endometrial secretion of prostaglandin (PG) F(2 alpha) during corpus luteum regression in swine but there is differential responsiveness to OT among endometrial cell types. To determine if progesterone influenced responsiveness of luminal epithelial, glandular epithelial, and stromal cells to 100 nM OT during luteolysis in swine, cells were isolated from endometrium of 15 gilts by differential enzymatic digestion and sieve filtration on day 16 postestrus and cultured continuously in the presence of 0, 10 or 100 nM progesterone. For phospholipase C (PLC) activity and PGF(2 alpha) secretion, stromal cells were most responsive to OT (P<0.01) in the absence of progesterone, whereas luminal epithelial cells were unresponsive and glandular epithelial cells displayed an intermediate response to OT (P<0.09). Progesterone enhanced PLC activity linearly in glandular epithelial cells (P<0.05) and influenced it quadratically in stromal cells (P=0.05). The effect of OT and progesterone on PLC activity in luminal epithelial cells was not significant, and progesterone did not increase PLC activity in response to OT in any cell type. Culture in the presence of progesterone, enhanced PGF(2 alpha) secretion in response to OT in luminal epithelial cells (P<0.05) but not in glandular epithelial or stromal cells. Progesterone also increased overall PGF(2 alpha) release from glandular epithelial (P<0.05) and stromal cells (P<0.06) across both levels of OT treatment. These results indicate that progesterone enhanced PGF(2 alpha) secretion from luminal epithelial cells in response to OT and increased basal PGF(2 alpha) release from glandular epithelial and stromal cells.     

Effects of nitric oxide and tumor necrosis factor-alpha on production of prostaglandin F2alpha and E2 in bovine endometrial cells

The purpose of this study was to determine whether nitric oxide (NO) mediates tumor necrosis factor (TNF)alpha influence on the bovine endometrium. TNFalpha influence on the bovine endometrium is limited to the stromal cells. Therefore, it was interesting to find out whether NO production by the stromal cells, stimulated by TNFalpha might influence the endometrial epithelium. Moreover, we investigated the intracellular mechanisms of TNFalpha- and NO-regulated prostaglandin (PG) F(2alpha) and PGE(2) synthesis. Epithelial and stromal cells from the bovine endometrium (Days 2-5 of the oestrous cycle) were separated by means of enzymatic dispersion and cultured for 6-7 days in 48-well plates. The confluent endometrial cells were exposed to a NO donor (S-NAP; 1-1000 microM) for 24 h. S-NAP strongly stimulated PGE(2) production in both bovine endometrial cell types (P<0.001). The effect of SNAP on PGF(2alpha) production was limited only to the stromal cells (P<0.05). To study the intracellular mechanisms of TNFalpha and NO action, stromal cells were incubated for 24 h with TNFalpha or S-NAP and with NO synthase (NOS) inhibitor (L-NAME; 10 microM) or an inhibitor of phosphodiesterase (IBMX; 10 microM). When the cells were exposed to TNFalpha in combination with NOS inhibitor (L-NAME), TNFalpha-stimulated PGs production was reduced (P<0.05). The inhibition of enzymatic degradation of cGMP by IBMX augmented the actions of S-NAP and TNFalpha on PGs production (P<0.05). The overall results suggest that TNFalpha augments PGs production by bovine endometrial stromal cells partially via induction of NOS with subsequent stimulation of NO-cGMP formation. NO also stimulates PGE(2) production in epithelial cells.     

Role of ovarian progesterone and potential role of prostaglandin F2alpha and prostaglandin E2 in modulating the uterine response to infectious bacteria in postpartum ewes

In sheep and cattle, the postpartum uterus is resistant to bacterial challenge until after corpora lutea develop. A 2 x 2 factorial arrangement of treatments was used to determine whether prostaglandins may mediate the effects of progesterone in transforming the postpartum uterus from resistant to susceptible. On d 14 postpartum, ewes (n = 6/group) were ovariectomized or sham ovariectomized, and the vena cava was catheterized for daily collection of uteroovarian-enriched blood. From d 15 to 20, ewes received twice daily intramuscular injections of progesterone in sesame oil or plain sesame oil. On d 20, each uterus received 75 x 10(7) cfu of Arcanobacterium pyogenes and 35 x 10(7) cfu of Escherichia coli. Uteri were collected on d 25 and examined for signs of infection. For each blood sample, unstimulated and mitogen-stimulated lymphocyte proliferation was measured as [3H]thymidine incorporation, smears were prepared for differential white blood cell (WBC) counts, and progesterone, prostaglandin F2alpha, (PGF2alpha), and prostaglandin E2 (PGE2) were quantified. All 12 progesterone-treated, but only two of the 12 oil-treated, ewes developed uterine infections (P < 0.001). Progesterone treatment increased (P < 0.001; 3.1 vs 1.5 ng/mL) and ovariectomy decreased (P < 0.001; 3.7 vs 0.9 ng/mL) vena caval progesterone. Progesterone treatment reduced (P < 0.01) PGF2alpha, (303.9 vs 801.3 pg/mL), and PGF2alpha was greater (P < 0.05) before than after inoculation (626.4 vs 478.8 pg/mL). The PGE2 concentration was greater in progesterone-treated, ovary-intact ewes than in ewes in the other groups (ovariectomy x progesterone treatment; P < 0.01). Ovariectomy increased (P < 0.005; 4.4 vs 2.9 pmol) and progesterone treatment decreased (P < 0.05; 3.2 vs 4.1 pmol) concanavalin A-stimulated lymphocyte proliferation. Ovariectomy increased lipopolysaccharides-stimulated proliferation (P < 0.05; 2.4 vs 1.9 pmol). For neutrophils per 100 WBC, the ovariectomy x progesterone and progesterone x period interactions were significant (P < 0.01). The ovariectomy x progesterone interaction was significant (P < 0.01) for lymphocytes per 100 WBC. Ovariectomy decreased monocytes (P < 0.001; 10 vs 13) and increased eosinophils (P < 0.001; 10 vs 5) per 100 WBC. Progesterone makes the postpartum uterus in ewes susceptible to infection, but ovariectomy allows ewes to remain resistant; uterine prostaglandins may mediate this change. This model creates opportunities to determine the mechanisms responsible for the shift from resistance to susceptible.