Effects of E2 levuglandins on the contractile activity of the rat uterus

The effects of E2 levuglandins on the contractile activity of rat uterine horns were studied. LGE2, AnLGE2, delta 9-LGE2 and the synthetic epimer, 8-epi-delta 9-LGE2 all induced contractions in a dose-response fashion. AnLGE2 gave decreased responses with increased bath concentrations. Paired comparisons showed potent and selective inhibitory effects of AnLGE2 on the uterotonic activity of prostaglandins. AnLGE2 inhibited the uterotonic activity of PGE2 at a 0.1:1 ratio, of PGD2 at a 1:1 ratio, but did not inhibit the activity of PGF2 alpha. Exposure of spontaneously contracting uteri to high concentrations of AnLGE2, or prolonged exposure to lower concentrations, suppressed contractions.     

Effect of beta-adrenergic stimulation on uterine contraction in response to arginine vasotocin and prostaglandin F2 alpha in the gecko Hoplodactylus maculatus.

The effects of beta-adrenergic stimulation on uterine contractions occurring in response to arginine vasotocin (AVT) and prostaglandin F2 alpha (PGF2 alpha) were compared during late pregnancy in the viviparous gecko Hoplodactylus maculatus. High doses of AVT (150 or 1,500 ng/g body weight) induced birth in vivo, but PGF2 alpha at doses of up to 2,000 ng/g did not induce birth. The effect of AVT (150 ng/g) on birth rate in vivo was not enhanced by pretreatment 20 min beforehand with the beta-adrenoreceptor antagonist dichloroisoproterenol (2 micrograms/g), whereas the effect of PGF2 alpha (200 ng/g) was markedly enhanced: geckos treated with dichloroisoproterenol and then with PGF2 alpha showed rapid birth-related behavior and gave birth. Isolated uteri showed a tonic contraction in response to AVT (100 ng/ml) and to PGF2 alpha (1,000 ng/ml). Pre-exposure of isolated uteri to the beta-adrenoreceptor agonist isoproterenol (1 microgram/ml) caused relaxation; this pre-exposure did not block the tonic contraction occurring in response to AVT, whereas it completely blocked the tonic contraction induced by PGF2 alpha. We conclude that in H. maculatus, beta-adrenergic stimulation inhibits uterine contractions induced by PGF2 alpha but not those induced by AVT. These data are the first to show that beta-adrenergic stimulation inhibits uterotonic responses to PGF2 alpha in a reptile, and they suggest that the cellular mechanisms by which AVT and PGF2 alpha induce contraction may differ in this species. They also provide further evidence for similarities between mammals and reptiles in the effects of beta-adrenergic stimulation on uterine relaxation.     

Transformation of prostaglandin D2 to isomeric prostaglandin F2 compounds by human eosinophils. A potential mast cell-eosinophil interaction

PGD2 undergoes extensive isomerization in vivo followed by metabolism by 11-ketoreductase to yield a family of biologically active isomeric PGF2 compounds, including 9, alpha 11 beta-PGF2. Because immunologically activated human mast cells produce substantial quantities of PGD2 and eosinophils accumulate around mast cells at sites of immediate hypersensitivity reactions, the ability of eosinophils to metabolize PGD2 was investigated. Purified human circulating eosinophils from four different donors transformed PGD2 to 9, alpha 11 beta-PGF2 and 12-epi-9 alpha, 11 beta-PGF2 in a time- and concentration-dependent manner. The formation of these compounds increased rapidly during the first 30 min of incubation of eosinophils with PGD2 and tended to plateau at approximately 2 h. Detection and quantification of the formation of 9 beta,11 beta-PGF2 and its 12-epi isomer was accomplished by a negative ion chemical ionization gas chromatography/mass spectrometry assay. On one occasion, eosinophils from one donor also transformed PGD2 to two additional isomeric PGF2 compounds, the stereochemical structures of which were not identified. The ability of eosinophils to produce PGD2 was then investigated. After stimulation with 2 microM A23187, the major cyclooxygenase product formed was thromboxane B2 (2247 pg/10(6) eosinophils) whereas only small quantities of PGD2 were produced (50 pg/10(6) eosinophils). Inasmuch as PGF2 compounds can exert biologic actions that differ from those of PGD2, this ability of eosinophils to transform PGD2 to PGF2 compounds could alter the local biologic effects of PGD2 released from adjacent mast cells and thus may represent a physiologically relevant mast cell-eosinophil interaction.     

Prostaglandin synthesis by the cochlea

The exogenous and endogenous syntheses of prostaglandins (PG's) by the cochlea of adult mongolian gerbils were studied in vitro. After incubation of the whole membraneous cochlea with [3H]-arachidonic acid (AA), syntheses of PGF2 alpha, 6-keto PGF1 alpha, PGE2, thromboxane (TX) P2 and PGD2 were evidenced in this order. The synthesis of radioactive PG's was almost completely inhibited by incubation with 10(-5) M indomethacin. No significant amounts of those PG's were detected by radioimmunoassay (RIA) in the cochlea obtained from animals killed by microwave irradiation at 5.0 kw for 0.8 sec. However, when the homogenate of the whole membraneous cochlea obtained from animals without microwave irradiation was incubated at 37 degrees C for 0-15 min, PGD2, PGE2, PGF2 alpha and 6-keto PGF1 alpha were found to be formed from endogenous AA in the cochlea by RIA. PG's were formed already at 0 time to considerable level (PGD2, PGF2 alpha and 6-keto PGF1 alpha, 90-120 pg/cochlea; PGE2, 370 pg/cochlea), reached to the maximum level (PGD2, PGF2 alpha and 6-keto PGF1 alpha, 170-200 pg/cochlea; PGE2, 500 pg/cochlea) at a 5-min incubation, and then gradually decreased. On the other hand, the amount of TXB2 was lower than the detection limit by RIA (less than 50 pg/cochlea) even after the incubation. The cochlea was dissected into three parts: organ of Corti + modiolus (OC + M), lateral wall (LW), and cochlear nerve (CN), and then PG's formed by these tissues were determined after a 5-min incubation of the homogenates. In the CN and OC + M, PGE2 was the major PG (100 and 160 pg/tissue, respectively), and the amounts of PGD2, PGF2 alpha and 6-keto PGF1 alpha were about 1/3 of those of PGE2. In the LW, the amounts of PGD2, PGE2, PGF2 alpha and 6-keto PGF1 alpha were about the same level (70-100 pg/LW).     

Evidence for separate PGD2 and PGF2 alpha receptors in the canine mesenteric vascular bed.

Potential interactions between PGD2 and PGF2 alpha in the mesenteric and renal vascular beds were investigated in the anesthetized dog. Regional blood flows were measured with electromagnetic flow probes. PGD2, PGF2 alpha and Norepinephrine (NE) were injected as a bolus directly into the appropriate artery, and responses to these agents were obtained before, during and after infusion of either PGD2 or PGF2 alpha into the left ventricle. In each case, the infused prostaglandin caused vascular effects of its own. Left ventricular infusion of PGD2 reduced responses to local injections of PGD2 in the intestine, and a similar effect was observed for PGF2 alpha, suggesting significant receptor or receptor-like interactions for each of the prostanoids. However, systemic infusion of prostaglandin F2 alpha (20--100 ng/kg/min) had no effect on renal or mesenteric vascular responses to local injection of prostaglandin D2. Similarly, PGD2 administration (100 ng/kg/min) did not affect responses to PGF2 alpha in the intestine. The present results therefore suggest that these prostaglandins, i.e., D2 and F2 alpha, act through separate receptors in the mesenteric and renal vascular beds. In addition, increased prostaglandin F2 alpha levels produced by infusion of F2 alpha reduced mesenteric but not renal blood flow, suggesting that redistribution of cardiac output might participate in side effects often observed with clinical use of this prostaglandin, such as nausea and abdominal pain.     

Prostaglandin D2 inhibits the proliferation of human malignant tumor cells

The cytotoxic effect of prostaglandin (PG) D2, PGE1 and PGF2 alpha was examined on human osteosarcoma cells (KSu cell line) in vitro, and PGD2 was most effective. DNA, RNA and protein syntheses of KSu cells were also found to be inhibited by PGD2 at a concentration of 5 micrograms/ml. Furthermore, the proliferation of various human malignant tumor cells was inhibited by PGD2 without exception so far. These results suggest that PGD2 shows an anti-neoplastic effect on a variety of human malignant tumor cells.     

Intraluteal infusions of prostaglandins of the E, D, I, and A series prevent PGF2 alpha-induced, but not spontaneous, luteal regression in rhesus monkeys

A luteotropic role for prostaglandins (PGs) during the luteal phase of the menstrual cycle of rhesus monkeys was suggested by the observation that intraluteal infusion of a PG synthesis inhibitor caused premature luteolysis. This study was designed to identify PGs that promote luteal function in primates. First, the effects of various PGs on progesterone (P) production by macaque luteal cells were examined in vitro. Collagenase-dispersed luteal cells from midluteal phase of the menstrual cycle (Day 6-7 after the estimated surge of LH, n = 3) were incubated with 0-5,000 ng/ml PGE2, PGD, 6 beta PGI1 (a stable analogue of PGI2), PGA2, or PGF2 alpha alone or with hCG (100 ng/ml). PGE2, PGD2, and 6 beta PGI1 alone stimulated (p less than 0.05) P production to a similar extent (2- to 3-fold over basal) as hCG alone, whereas PGA2 and PGF2 alpha alone had no effect on P production. Stimulation (p less than 0.05) of P synthesis by PGE2, PGD2, and 6 beta PGI1 in combination with hCG was similar to that of hCG alone. Whereas PGA2 inhibited gonadotropin-induced P production (p less than 0.05), that in the presence of PGF2 alpha plus hCG tended (p = 0.05) to remain elevated. Second, the effects of various PGs on P production during chronic infusion into the CL were studied in vivo. Saline with or without 0.1% BSA (n = 12), PGE2 (300 ng/h; n = 4), PGD2 (300 ng/h; n = 4), 6 beta PGI1 (500 ng/h; n = 3), PGA2 (300 ng/h; n = 4), or PGF2 alpha (10 ng/h; n = 8) was infused via osmotic minipump beginning at midluteal phase (Days 5-8 after the estimated LH surge) until menses. In addition, the same dose of PGE, PGD, PGI, or PGA was infused in combination with PGF2 alpha (n = 3-4/group) for 7 days. P levels over 5 days preceding treatment were not different among groups. In 5 of 8 monkeys receiving PGF2 alpha alone, P declined to less than 0.5 ng/ml within 72 h after initiation of infusion and was lower (p less than 0.05) than controls. The length of the luteal phase in PGF2 alpha-infused monkeys was shortened (12.3 +/- 0.9 days; mean +/- SEM, n = 8; p less than 0.05) compared to controls (15.8 +/- 0.5). Intraluteal infusion of PGE, PGD, PGI, or PGA alone did not affect patterns of circulating P or luteal phase length.(ABSTRACT TRUNCATED AT 400 WORDS)     

Proliferative effect of PGD2 on osteoblast-like cells; independent activation of pertussis toxin-sensitive GTP-binding protein from PGE2 or PGF2 alpha.

PGD2 stimulated DNA synthesis and decreased alkaline phosphatase activity dose-dependently between 10 nM and 10 microM in osteoblast-like MC3T3-E1 cells. PGD2 had little effect on cAMP production, but caused very rapid enhancement of phosphoinositide (PI) hydrolysis dose-dependently between 10 nM and 10 microM. The formation of inositol trisphosphate (IP3) induced by PGD2 reached the peak within 1 min and decreased thereafter, which is more rapid than that induced by PGE2 or PGF2 alpha and both PGE2 and PGF2 alpha affected PGD2-induced IP3 formation additively. Pertussis toxin (PTX) inhibited both PGD2-induced formation of inositol phosphates and DNA synthesis. The degree of these PTX (1 micrograms/ml)-induced inhibitions was similar. In addition, neomycin, a phospholipase C inhibitor, inhibited PGD2-induced DNA synthesis as well as the formation of IP3, and the patterns of both inhibitions were similar. In the cell membranes, PTX-catalyzed ADP-ribosylation of a 40-kDa protein was significantly attenuated by pretreatment of PGD2. Time course of the attenuation of PTX-catalyzed ADP-ribosylation by PGD2 was apparently different from that by PGE2 or PGF2 alpha. These results indicate that PGD2 activates PTX-sensitive GTP-binding protein independently from PGE2 or PGF2 alpha and stimulates PI hydrolysis resulting in proliferation of osteoblast-like cells.     

Determination of prostaglandin F2 alpha, E2, D2 and 6-keto-F1 alpha in human cerebrospinal fluid.

Prostaglandin (PG)F2 alpha, E2, D2 and 6-keto-F1 ALha were determined in human cerebrospinal fluid by a mass spectrometric technique. The samples were obtained from 12 patients with suspected intracranial disease. A 64 fold variation in PG levels was observed. The major PG was 6-keto-F1 alpha (0.12--15 ng/ml). PGF2 alpha and PGE2 were present in lower concentrations PGD2 was below the level of detection (0.05 ng/ml) except in one patient with extremely high total levels of PGs.     

Late-Phase Accumulation of Inositol Phosphates Stimulated by Prostaglandins D2 and F2α in Neuroblastoma × Glioma Hybrid NG108-15 Cells

The accumulation of inositol phosphates (IPs) in response to prostaglandins (PGs) was studied in NG108-15 cells preincubated with myo-[3H]inositol. As a positive control, bradykinin caused accumulation of IPs transiently at an early phase (within 1 min) and continuously during a late phase (15-60 min) of incubation in the cells. PGD2 and PGF2 alpha did not significantly cause the accumulation of IPs at an early phase but significantly stimulated inositol bisphosphate (IP2) and inositol monophosphate (IP) formation at late phase of incubation. The maximum stimulation was obtained at greater than 10(-7) M concentrations of these PGs, the levels being three-and twofold for IP2 and IP1, respectively. 9 alpha, 11 beta-PGF2 has a slight effect but PGE2 and the metabolites of PGD2 and PGF2 alpha have no effect up to 10(-6)M. The effects of PGD2 and PGF2 alpha were not additive, but the effect of each PG was additive to that of bradykinin at a late phase of incubation. Inositol 1-monophosphate was mainly identified in the stimulation by 10(-5) M PGD2 and 10(-5) M PGF2 alpha, whereas both inositol 1-monophosphate and inositol 4-monophosphate were produced in the stimulation by 10(5) M bradykinin. Depletion of extracellular Ca2+ diminished the stimulatory effect of PGD2 and PGF2 alpha and late-phase effect of bradykinin, but simple Ca2+ influx into the cells by high K+, ionomycin, or A23187 failed to cause such late-phase effects. These results suggest that PGD2 and PGF2 alpha specifically stimulate hydrolysis of inositol phospholipids.     

Temporal changes in serum prostaglandin F2alpha and oxytocin in dairy cows with short luteal phases after the first postpartum ovulation

Luteolysis in the cow depends upon an interaction between prostaglandin F(2alpha) (PGF(2alpha)) and oxytocin. The objectives of our study were 1) to determine oxytocin concentrations in postpartum dairy cows and 2) to identify the temporal relationship between oxytocin and PGF(2alpha) release patterns during luteolysis in normal and abbreviated estrous cycles in the postpartum period. Serum oxytocin and PGF(2alpha) metabolite (PGFM) concentrations from nine cows which had short estrous cycles (< 17 d) were compared with those of six cows which had normal estrous cycles. Serum basal oxytocin concentrations in short estrous cycle cows (23.7 to 31.1 pg/ml) were higher (P<0.05) than those of normal estrous cycle cows (14.6 to 19.8 pg/ml). Oxytocin concentrations increased to peak values in both short and normal cycle cows, during luteolysis. Basal PGFM concentrations (112.2 to 137.4 pg/ml) were higher in cows with short cycle (P<0.05) than in cows with normal cycles (62.9 to 87.5 pg/ml). The increase in PGFM concentrations during luteolysis was significant in both normal cycle and short cycle cows (P<0.05). Increases in serum PGFM concentrations were always associated with increases in serum oxytocin concentrations in normal cycle and short cycle cows and the levels decreased simultaneously before the subsequent estrus. Results support the idea of a positive relationship between PGF(2alpha) and oxytocin concentration during the estrous cycle as well as a possible synergistic action of these hormones in the induction of luteolysis in dairy cattle.     

Plasma 13,14-dihydro-15-keto-PGF alpha (PGFM) in pregnant and nonpregnant heifers prior to and during surgery and following intrauterine injection of PGF2 alpha

On day 17 postestrus or postmating, heifers were given intrauterine injections of saline (2 pregnant, 2 non-pregnant) or 200 micrograms PGF2 alpha (7 pregnant, 6 nonpregnant) through cannulae installed surgically into the uterine horn ipsilateral to the corpus luteum bearing ovary. Jugular blood samples were collected prior to the laparotomy at which the cannulae were installed during surgery, and for 90 min following the intrauterine injection. Plasma was assayed for progesterone and 13,14-dihydro-15-keto-PGF2 alpha (PGFM). Laparotomies were reopened to confirm proper cannula placement and to determine if blastocysts were present in mated heifers. Concentrations of PGFM were higher in pregnant compared to nonpregnant heifers during the presurgery (68 +/- 26 vs 24 +/- 26 pg/ml; P less than .025) and surgery (186 +/- 47 vs 65 +/- 17 pg/ml; P less than .05) periods. Pregnancy status did not alter the mean concentrations of PGFM (pregnant, 554 +/- 70 pg/ml; nonpregnant, 422 +/- 81 pg/ml) or the half-life of its decline in concentration (18 min) following intrauterine injection of PGF2 alpha. Pregnancy at 17 days in cattle does not appear to influence PGF2 alpha transport from the uterine lumen or its metabolism in the uterus or elsewhere in response to an acute intrauterine injection.     

Transport of uterine PGF2 alpha to the ovaries by systemic circulation and local lymphovenous-arterial diffusion during luteolysis in sheep.

The theory of countercurrent vascular transfer of PGF2 alpha during luteolysis was examined. In the first experiment, pulmonary clearance of PGF2 alpha was determined to re-examine whether the total amount of PGF2 alpha was degraded in the lungs after one passage. Cardiac output was measured by the Fick method and PGF2 alpha by radio-immunoassay before and after vascular lung supply, using pulmonary catheterization and the interventional radiology method in ten anaesthetized ewes on day 16 of the oestrous cycle. Cardiac output remained stable (7156 +/- 439 ml min-1). Infusion of 5 iu oxytocin resulted in an increase in plasma PGF2 alpha concentrations at 30 min in the uterine vein and the pulmonary and femoral arteries (3811 +/- 806, 224 +/- 55 and 18 +/- 4 pg ml-1, respectively). The PGF2 alpha concentrations decreased exponentially and the half-time decreases were 27 (r = 0.99), 16 (r = 0.99) and 18 (r = 0.98) min, respectively. Pulmonary clearance of PGF2 alpha was estimated at 6338 +/- 451 ml min-1. In a second experiment, an arterio-arterial gradient of plasma PGF2 alpha concentrations was analysed between the proximal and distal segments of the ovarian artery to verify whether the total amount of PGF2 alpha flowing to the ovary was from the local venous-arterial countercurrent pathway. Surgical catheterization techniques were performed on 11 ewes on day 16 of the oestrous cycle. The ovarian arterial blood flow was measured by the implantable Doppler method (8 +/- 1 ml min-1). The maximum plasma PGF2 alpha concentrations in the femoral and distal ovarian arteries were 23 +/- 6 and 42 +/- 11 pg ml-1 (P < 0.05), respectively. Plasma PGF2 alpha decreased exponentially in the femoral artery and the half-time decrease was 26 min (r = 0.98), and in the distal ovarian artery close to the ovary PGF2 alpha decreased linearly and the half-time decrease was 108 min (r = 0.96). Consequently, the arterio-arterial diffusion gradient of PGF2 alpha concentrations was extended to 3 h. These experiments showed that the PGF2 alpha flow rate in the pulmonary artery was 42.275 +/- 10.793 micrograms per 150 min (n = 10) and the systemic arterial PGF2 alpha flow rate was 5.359 +/- 1.658 micrograms per 150 min (n = 10). Therefore, 12% of the PGF2 alpha was not oxidized by the lungs. The proximal ovarian PGF2 alpha flow rate was 6.909 +/- 2.341 ng per 150 min, while the distal flow rate was 21.003 +/- 5.703 ng per 150 min (n = 11). Thus, 33% of the PGF2 alpha was transported rapidly to the ovary via the systemic route, while 67% was transported by slow local countercurrent diffusion, which extended the duration of luteolytic activity to four times that of the PGF2 alpha surge. These results indicate both rapid systemic transport of PGF2 alpha to the ovaries and a slower buffer mechanism involving a local diffusion pathway, rather than a direct countercurrent system.     

Secretion of PGF2alpha and oxytocin during hyperthermia in cyclic and pregnant heifers

The effects of acute heat stress (HS) and oxytocin (OT) injection on plasma concentrations of PGF2alpha and OT were examined in cyclic (C; n = 15) and pregnant (P; n = 11) dairy heifers. On Day 17 of synchronized estrous cycles, animals were randomly assigned to either thermoneutral (TN; 20 degrees C, 20% RH) or HS (42 degrees C, 60% RH) chambers. The jugular vein of each heifer was cannulated and blood samples collected hourly for 4 h, then every 15 min for an additional 3 h. Oxytocin (100 IU) was injected (IV) 5 h after the start of blood collection. Plasma samples were assayed subsequently for concentrations of 13,14-dihydro-15-keto PGF2alpha (PGFM) and OT. During the 7-h experiment, body temperature of HS heifers reached 41.2 degrees C as compared to 38.5 degrees C in control heifers. Plasma concentrations of PGFM increased (P<0.05) and peaked 30 min after OT injection in C (890 pg/ml) and P (540 pg/ml) heifers. In C heifers, heat stress failed to alter PGFM concentrations either before or after OT injection. In the P group, PGFM concentrations following OT injection tended to be higher in HS heifers were further TN heifers (peak values of 690 vs. 410 pg/ml). Pregnant TN and HS heifers were further classified as responders or non-responders to OT challenge according to a cutoff value for PGFM of 193 pg/ml (overall mean of C heifers minus 1 SD). Five of six HS and one of five TN pregnant heifers were classified as responders (P<0.06). Oxytocin concentrations in plasma prior to injection of exogenous OT were not affected by HS or pregnancy status. It is concluded that in C heifers, acute HS in vivo does not cause any further rise in PGF2alpha secretion. However, in P heifers, HS appears to antagonize suppressive effects of the embryo on uterine secretion of PGF2alpha, as indicated by the larger proportion of P heifers responding to OT challenge.     

Prostaglandin F in reproductive tissues collected during the luteal phase of the estrous cycle and at parturition in Virginia opossums (Didelphis virginiana )

Prostaglandin F(2alpha) (PGF(2alpha)) plays a role in the regression of the corpus luteum (CL) in a number of placental mammals. However, the mechanism of luteal regression has not been extensively studied in marsupials. The objectives of this study were to characterize changes in concentrations of PGF(2alpha) within utero-ovarian (UO) tissue/venous plasma during the luteal phase of the estrous cycle in Virginia opossums, to correlate these changes with those of plasma progesterone (P(4)), and to characterize the peripheral pattern of 13,14-dihydro-15-keto-PGF(2alpha) (PGFM) in parturient opossums. Ovaries, uteri, UO venous plasma and peripheral plasma were collected on Days 5, 9 and 12 after induced ovulation (n = 3 to 4 opossums/group). In addition, concentrations of PGFM were measured in peripheral plasma collected from two opossums during late gestation (Days 7,9,11 and 12) and at parturition (Day 13). Concentrations of P(4), PGFM and PGF(2alpha) in tissue homogenates and plasma samples were estimated by radioimmunoassay. In nonpregnant opossums, peripheral P(4) levels were highest on Day 5 (38.8 +/- 11.1 ng/ml, x +/- SEM) declined on Day 9 (22.6 +/- 7.4 ng/ml), and were at basal levels by Day 12 (2.4 +/- 0.7 ng/ml). Endometrial concentrations of PGF(2alpha) increased (P = 0.056) from Day 5 (15.7 +/- 4.1 ng/g) to Day 9 (92.1 +/- 61.0 ng/g) and were maintained to Day 12 (97.2 +/- 25.7 ng/g). Prostaglandin F(2alpha) concentrations in UO plasma increased (P < 0.01) from Day 5 (143.1 +/- 32.7 pg/ml) to Day 12 (333.0 +/- 32.4 pg/ml). Prostaglandin F(2alpha) concentrations in ovarian tissue followed a similar pattern and were correlated with UO concentrations (r = 0.708, P < 0.05). In pregnant opossums, the highest levels of peripheral PGFM were recorded in the peripartum period, when luteal regression would also be expected to occur. The negative temporal relationship between peripheral concentrations of P(4) and concentrations of PGF(2alpha) in UO tissue/venous plasma observed in this preliminary study is consistent with the notion that PGF(2alpha) from the ovary and/or uterus may play a role in CL regression in the opossum.     

On the role of 'in vivo' injected progesterone and of the 'in vitro' presence of oxytocin, modulating Ca2+ uptake by the rat uteri from spayed animals and as controllers of the production of arachidonic acid metabolism.

We attempted to explore possible mechanism(s) subserving the influence of oxytocin (O) and of progesterone (P) in the isolated rat uterus studying the action of these hormones on: the synthesis and release of prostaglandins (PGs), the metabolism of labelled arachidonic acid and the uptake of Ca2+ by the tissue from ovariectomized animals. The experiments were done with uterine preparations isolated from spayed rats treated or not with P prior to sacrifice and afterward incubated or not with O 'in vitro'. While uterine strips from untreated spayed rat uterus exhibited a basal release into the incubating medium of approximately the same amounts of PGF2 alpha, and PGE2, the 'in vitro' addition of O (50 mU/ml) increased significantly (p < 0.05) the output of PGF2 alpha without changing the release of PGE2. In tissue from rats injected with P prior to sacrifice the output of PGF2 alpha rose significantly (p < 0.01) as it did after the addition of O to preparations obtained from spayed rats treated with P in comparison to findings in uteri from spayed rats but not in comparison to uteri from spayed rats treated with P alone. Moreover, the 'in vitro' addition of O (50 mU/ml) only increased the formation of PGF2 alpha (p < 0.05) and of 5-HETE (p < 0.05); nevertheless the administration of P to spayed rats diminished significantly (p < 0.05) the formation of 6-keto-PGF1 alpha from uteri, but increased that of PGF2 alpha (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prostaglandin F2 alpha-stimulated release of ovarian oxytocin in the sheep in vivo: threshold and dose dependency

To determine the threshold of prostaglandin F2 alpha (PGF2 alpha)-stimulated oxytocin secretion from the ovine corpus luteum, low levels of PGF2 alpha (5-100 pg/min) were infused into the ovarian arterial blood supply of sheep with ovarian autotransplants. PGF2 alpha was infused for six sequential 10-min periods at hourly intervals, 6, 12, or 24 days after estrus (n = 3 for each day). Each cycle day was studied during a separate cycle. Oxytocin and progesterone in ovarian venous and carotid arterial plasma was measured by radioimmunoassay, and secretion rates were determined (venous-arterial concentration x plasma flow). In animals treated on Day 6, 5 pg/min PGF2 alpha caused a significant release of oxytocin (p less than 0.01), whereas in animals treated on Day 12, this threshold was 40 pg/min (p less than 0.05). In animals treated on Day 24, the threshold for oxytocin release was greater than 100 pg/min. PGF2 alpha did not significantly change ovarian blood flow or progesterone secretion rate on any day (p greater than 0.05). To determine residual luteal oxytocin after each threshold experiment, 5 mg PGF2 alpha was given i.m. to all animals. Significantly more oxytocin was released by Day 6 than by Day 12 and Day 24 corpora lutea, and by Day 12 than by Day 24 corpora lutea (1.2 micrograms, 0.7 microgram, and 0.3 microgram, respectively; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Estrogens and prostaglandin F2alpha in the semen and blood plasma of stallions

A study was performed to determine the levels of estrogens and prostaglandin F(2)alpha in the stallion ejaculate. Simultaneous semen and blood plasma samples were collected from 19 stallions, 2 weeks apart, during the breeding season. Although not statistically different, the total mean estrogen content tended to be higher in seminal plasma (4447 pg/ml) than in blood (2497 pg/ml). A tendency was found for higher mean estrone sulphate concentrations than for total free steroid in both seminal (4116.1 vs 330.5 pg/ml) and blood plasma (2447.1 vs 49.5 pm/ml). Mean concentrations of estrone in ejaculate and blood plasma were 257.1 +/- 267.0 (SD) and 9.5 +/- 5.4 pg/ml, respectively. Estradiol-17beta concentrations were 73.4 +/- 87.4 and 40.0 +/- 27.6 pg/ml in ejaculates and blood plasma, respectively. Mean PGF(2)alpha concentrations tended to be much higher than total estrogens (1106.8 +/- 1636.4, SD, vs approximately 260 ng/ejaculate, respectively). To our knowledge this is the first report of PGF(2)alpha and estrogen concentrations in the stallion ejaculate.     

Role of COX-1 and COX-2 on skin PGs biosynthesis by mechanical scratching in mice

We examined the involvement of cyclooxygenase (COX)-1 and COX-2 on mechanical scratching-induced prostaglandins (PGs) production in the skin of mice. The dorsal regions of mice were scratched using a stainless brush. COXs expressions in the skin were analyzed using real-time PCR and Western blotting. The effect of acetylsalicylic acid (ASA) on the ability of PGs production were determined based on skin PGs level induced by arachidonic acid (AA) application. Mechanical scratching increased PGD2, PGE2, PGI2 and PGF(2 alpha). COX-1 was constitutively expressed and COX-2 expression was enhanced by scratching. Intravenous administration of ASA inhibited PGs biosynthesis in the normal skin. PGs levels of the skin 6h after ASA administration (ASA 6 h) were almost equal to those of the skin 10 min after ASA administration (ASA 10 min). In the scratched skin, AA-induced PGE2 and PGI2 of ASA 6 h were significantly higher than those of ASA 10 min. The skin PGD2 and PGF(2 alpha) of ASA 10 min were almost same to those of ASA 6 h. In the normal skin of COX-1-deficient mice, skin PGD2 level was lower than that of wild-type mice, although PGE2, PGI2 and PGF(2 alpha) levels were almost equal to those of wild type. In the scratched skin of COX-1-deficient mice, PGD2, PGE2, PGI2 and PGF(2 alpha) levels were lower than those of wild-type mice. These results suggested that cutaneous PGD2 could be mainly produced by COX-1, and PGE2 and PGI2 could be produced by COX-1 and COX-2, respectively, in mice.     

Prostaglandin F2 alpha as the luteolysin in swine: VI. Hormonal regulation of the movement of exogenous PGF2 alpha from the uterine lumen into the vasculature

To test the endocrine-exocrine theory of maternal recognition of pregnancy in the pig 16 gilts were assigned randomly to a 2 X 2 factorial involving pretreatment with sesame oil (SO) or estradiol valerate (5 mg; EV) injected on Days 11 through 14 of the estrous cycle and an intrauterine injection of saline (5 ml; SA) or prostaglandin F2 alpha (50 micrograms; PGF) on Day 14. Peripheral blood samples were collected for 120 min postinjection and analyzed for 15-keto-13,14-dihydro-PGF2 alpha (PGFM). PGFM concentrations were lower in EV than SO gilts (438 vs. 844 pg/ml; p less than 0.05). There was heterogeneity of regression between EV and SO gilts (p less than 0.01), with EV gilts having a slower release of PGF from the uterine lumen into the vasculature. Prostaglandin F2 alpha did not increase mean PGFM concentrations (p greater than 0.10), but resulted in an altered temporal pattern of PGFM (p less than 0.05) compared to SA gilts. There was an interaction between the two treatments over time, with EV-PGF gilts demonstrating a slower, more gradual release of PGFM than SO-PGF gilts. To test whether prostaglandins of the E series were involved in this mechanism, gilts were assigned to two 4 X 4 latin squares balanced for residual effects and treated with saline or flunixen meglumine (Banamine). Each gilt was treated with four PGE:PGF infusion sequences (SEQ) in each uterine horn: phosphate-buffered saline (PBS; PBS-SEQ), PGE1 (50 micrograms), PGE2 (50 micrograms), and PGE1 (25 micrograms) + PGE2 (25 micrograms) (PGE-SEQ), with each infusion followed 15 min later by PGF (25 micrograms).(ABSTRACT TRUNCATED AT 250 WORDS)