The effect of locally administered PGE2 on the contractility of the nonpregnant human uterus in vivo

The effect of locally administered prostaglandin E₂ on the sensitivity and reactivity of the nonpregnant human uterus during the menstrual cycle was studied in seven women. An increase in uterine contractility in response to as little as 0.25 μg PGE₂ could be observed during both the mid-proliferative and mid-secretory phases of the menstrual cycle, but around ovulation a marked decrease in sensitivity to PGE₂ was noted. An inhibition of uterine motility was observed during menstruation in response to 30–40 μg PGE₂. Endogenous E prostaglandin normally occurs in the secretory endometrium in levels comparable to the amount of exogenous PGE₂ which elicited increased or decreased uterine activity in this study. These findings suggest that PGE₂ may play an important role in the cyclical regulation of uterine motility during the menstrual cycle.     

The effect of locally administered PGE2 on the contractility of the nonpregnant human uterus in vivo

The effect of locally administered prostaglandin E₂ on the sensitivity and reactivity of the nonpregnant human uterus during the menstrual cycle was studied in seven women. An increase in uterine contractility in response to as little as 0.25 μg PGE₂ could be observed during both the mid-proliferative and mid-secretory phases of the menstrual cycle, but around ovulation a marked decrease in sensitivity to PGE₂ was noted. An inhibition of uterine motility was observed during menstruation in response to 30–40 μg PGE₂. Endogenous E prostaglandin normally occurs in the secretory endometrium in levels comparable to the amount of exogenous PGE₂ which elicited increased or decreased uterine activity in this study. These findings suggest that PGE₂ may play an important role in the cyclical regulation of uterine motility during the menstrual cycle.     

The effect of locally administered PGF2α on the contractility of the nonpregnant human uterus in vivo

The effect of locally administered prostaglandin F_2α on the sensitivity and reactivity of the nonpregnant human uterus during the menstrual cycle was studied. An increase in uterine contractility in response to as little as 1.0 μg PGF_2α could be observed in all patients during both the early and late portions of the menstrual cycle, but at the time of ovulation a marked decrease in sensitivity was noted. Endogenous prostaglandin normally occurs in the secretory endometrium in levels compatible with the amount of exogenous prostaglandin which elicited increased uterine activity. These findings support the hypothesis that PGF_2α plays an important physiological role in the cyclical regulation of uterine motility during the human menstrual cycle.     

The effect of locally administered PGE2 on the contractility of the nonpregnant human uterus in vivo.

The effect of locally administered prostaglandin E2 on the sensitivity and reactivity of the nonpregnant human uterus during the menstrual cycle was studied in seven women. An increase in uterine contractility in response to as little as 0.25 mug PGE2 could be observed during both the mid-proliferative and mid-secretory phases of the menstrual cycle, but around ovulation a marked decrease in sensitivity to PGE2 was noted. An inhibition of uterine motility was observed during menstruation in response to 30--40 mug PGE2. Endogenous E prostaglandin normally occurs in the secretory endometrium in levels comparable to the amount of exogenous PGE2 which elicited increased or decreased uterine activity in this study. These findings suggest that PGE2 may play an important role in the cyclical regulation of uterine motility during the menstrual cycle.     

In vivo inhibition of the human non-pregnant uterus by prostaglandin E2

The discrepancy between the effect of PGE₂ on the non-pregnant myometrium (relaxation) as compared to (stimulation) has not yet been solved. Nine women in the early post-menopause volunteered for the investigation. Prostaglandin (PG) F_2α or E₂ was administered either by single intravenous (i.v.) injection or by intra-uterine instillation and the uterine contractility was recorded by the microballoon technique. The response of the menopausal uterus to i.v. injections of PGF_2α or PGE₂ was characterized by rapid stimulation while intra-uterine instillation of PGF_2α induced gradual but sustained elevation of uterine tonus. However, the intra-uterine injection of PGE₂ caused inhibition of different components of uterine contractility. The fact that PGE₂ can also inhibit the motility of the menopausal non-pregnant uterus coincides with earlier results i.e. the discrepancy may not exist. Moreover, in one cycling patient (13–18th days of the menstrual cycle) similar results were also obtained. Two theories were offered to explain why PGE₂ stimulated the uterus when given as a single i.v. injection but inhibited the same organ when instilled locally into the uterine cavity.     

Further evidence for role of leukotrienes as mediators of decidualization in the rat

Inhibitors of leukotrieens were utilized to investigate the role of leukoteines (LTs) in the induction of decidualization in the rat. Alzet osmotic minipumps, filled with either FPL 55712 (FPL, a specific antagonist of peptidoleukotrienes), nordihydroguaiaretic acid (NDGA, an inhibitor of LT synthesis) or in combination with leukotriene C₄ (LTC₄) and/or prostaglandin E2 (PGE₂), were instilled at the ovarian end of uterine horns of day 5 pseudopregnant rats. Intraluminal infusion of FPL or DNGA, for 4 days, induced a dose dependent decrease in the uterine wet weights when compared to that induced by the infusion of their corresponding vehicles (1 μl/h). Furthermore, simultaneous infusion of LTC₄ (10 ng/h) with different doses of FPL (1, 0.5, or 0.25 μg/h) produced an increase in uterine weights as compared to that produced by FPL alone. Maximum response, however, was noted when LTC₄ (n0 ng/h) was infused with FPL at a rate of 0.5 μg/h. The infusion of LTC₄ (10 ng/h) or PGE₂ (1 μg/h) with NDGA, at 1 and 5 μg/h, could not overcome its inhibitory effect on decidualization. On the contrary, a combination of LTC₄ (10 ng/h) and PGE₂ (1 μg/h) was comparable to that induced by the infusion of the vehicle. To determine if the synthesis of PGs and LTs was inhibited by NDGA, one uterine horn was infused with NDGA (5 μg/h) and the other horn with the vehicle. The intrauterine infusion of NDGA for 24 h inhibited the release of PGE₂, PGF_2α, LTC₄ and LTB₄ as compared to those released by the vehicle-infused horns. These data suggest that both PGs and LTs are required for the induction and progression of decidualization.     

PGE2 and dibutyryl-cAMP enhance the response of rat granulosa cells to FSH

Granulosa cells isolated from immature Sprague-Dawley rat ovaries produce progesterone (31.7 pg/μg cell protein) in response to an acute FSH stimulus (5 μg/ml NIH-FSH-S11, 2 h). After culture for 48 h in the absence of hormones (control culture), progesterone production by the granulosa cells in response to FSH is significantly reduced (2.9 pg/μg cell protein). Cells cultured with prostaglandin E₂ (PGE₂, 1 μg/ml) or dibutyryl-cAMP (dbcAMP, 1 mM) exhibited a discernibly greater steroidogenic response to FSH (12.5 and 53.4 pg/μg cell protein, respectively) than that of control cultures. Therefore the presence of PGE₂ or dbcAMP in the culture medium helps to maintain the steroidogenic capacity of granulosa cells in culture. It is probable that this capacity is maintained at a locus distal to the production of cAMP by FSH.Paradoxically, granulosa cells cultured with PGE₂ produce less cAMP in response to FSH stimulation than cells in control cultures (15.9 250.3 fm/μg cell protein). This may be due to a suppressive effect of prior exposure to PGE₂ on the subsequent activity of adenylate cyclase when the FSH is introduced and a concomitant elevation of phosphodiesterase activity.     

Effect of indomethacin and 7-oxa-13-prostynoic acid on luteinization of transplanted rat ovarian follicles induced by luteinizing hormone and prostaglandin E2

The ability of prostaglandin E₂ (PGE₂) to initiate luteinization was demonstrated using a system of in vitro incubation of ovarian follicles followed by transplantation. Follicles from diestrous rats were incubated with 0.05 to 50 μg/ml PGE₂, 10 μg/ml luteinizing hormone (LH), or alone in Krebs-Ringer bicarbonate buffer plus glucose for 2 hr. Then follicles were transplanted under the kidney capsules of hypophysectomized recipients, with follicles exposed to PGE₂ on one side and those exposed to LH or buffer only on the other side. As determined at autopsy 4 days later and confirmed by histological examination, follicles exposed to PGE₂ at concentrations of 0.5 μg/ml or greater, or to LH, transformed into corpora lutea, but control follicles regressed. Incubation of follicles with LH in the presence of indomethacin, an inhibitor of prostaglandin synthesis, significantly reduced the incidence of luteinization. Prostaglandin E₂ (10 μg/ml) was able to override the inhibition of luteinization by indomethacin (150 μg/ml). The prostaglandin analogue 7-oxa-13-prostynoic acid (100 μg/ml) failed to prevent luteinization in response to either 5 μg/ml LH or 1 μg/ml PGE₂. Results with PGE₂ and with indomethacin suggest a role for prostaglandins in the luteinizing action of LH.We have reported previously that in vitro exposure of diestrous rat follicles to luteinizing hormone (LH) will result in transformation of the follicles to corpora lutea following transplantation under the kidney capsules of hypophysectomized rats. Dibutyryl cyclic AMP (DBC) mimics this effect of LH, and transplants produce progesterone in measurable amounts after both LH and DBC exposure when prolactin is administered in vivo to recipients.Kuehl et al. have suggested that prostaglandins may act as obligatory intermediates in the effect of LH on the ovary, acting between LH and adenylate cyclase. Preliminary results indicated that prostaglandin E₂ (PGE₂) could induce luteinization in our system. The extent of prostaglandin involvement in luteinization was further investigated in this work, using two reported antagonists of prostaglandin action, indomethacin and 7-oxa-13-prostynoic acid. Indomethacin has been found to inhibit synthesis of prostaglandins E₂ and F_2α; 7-oxa-13-prostynoic acid, which acts as a competitive antagonist of prostaglandins, prevented the effect of LH and prostaglandins E₁ and E₂ on cyclic AMP production in mouse ovaries.     

Sparing effects of intrauterine treatment with prostaglandin E2 on luteal function in cycling gilts

Twelve crossbred gilts, 8 to 9 months of age, were used to study the effects of prostaglandin E₂ (PGE₂) on luteal function during the estrous cycle. Intrataurine and jugular vein catheters were surgically placed before day 7 of the treatment estrous cycle and gilts were randomly assigned to 1 or 3 treatment groups. Groups I and II received constant intrauterine infusion of vehicle (6.0 ml/24 hr) or PGE₂ (2400 μg/day; 6.0 ml/24 hr) respectively; while group III was given intrauterine infusions of 400 μg PGE₂ every 4 hr. All infusions were initiated on day 7 and continued until estrus or through day 23. Jugular blood samples were collected twice daily from days 7 to 30 for progesterone analysis. Intrauterine infusion of PGE₂ at the dose and frequencies given in this study delayed the decline in jugular plasma progesterone and resulted in prolongation of the estrous cycle length. The results of this study have shown that PGE₂ at the dosage and frequency of administration used was capable of extending corpus luteum function.     

The effect of physiological levels of non-esterified fatty acids on the radioimmunoassay of prostaglandins

Non-esterified fatty acids (NEFA) can significantly interfere with the radioimmunoassay of PGE and PGF_2α using commercially available anti-sera. PGB₁ antigen-antibody binding is 50% inhibited by 110 pg of PGB₁, 48 ng of PGE₁, 3.5 μg of PGF_2α, or 9.0 μg linoleic, 14 μg arachidonic, 22 μg δ-linoleic, 40 μg palmitoleic or 45 μg oleic acids. PGF_2α antigen-antibody binding is 50% inhibited by 270 pg of PGF_2α, 70 ng of PGE₁, or 4.2 μg arachidonic, 14 μg δ-linolenic, 22 μg linoleic, 70 μg palmitoleic or 110 μg oleic acids. Physiological levels of NEFA, such as the quantities found in small volumes of plasma, are sufficient to prohibit accurate prostaglandin measurements. Chromatography on small columns of silicic acid proved to be an effective technique for separation of NEFA and prostaglandin from lipid extracts, however, the results of this study suggest that the interference produced by the presence of NEFA in the measurement of prostaglandin from certain physiological fluids may be avoided if the prostaglandins are not extracted prior to radioimmunoassay.     

Effects of hydrocortisone, oestradiol and progesterone on A23187-stimulated prostaglandin output from the guinea-pig uterus superfused in vitro

Hydrocortisone (10 μg/ml) had no effect on the basal outputs and A23187-stimulated outputs of PGF_2α, PGE₂ and 6-keto-PGF_1α from the Day 15 guinea-pig uterus superfused . These findings indicate that the high output of PGF_2α from the guinea-pig uterus during the last one-third of the oestrous cycle is not modulated by the adrenal glucocorticoid hormones. Progesterone (10 gmg/ml) had no effect on the A23187-induced increases in PG output from the Day 15 guinea-pig uterus. However, oestradiol (10 gmg/ml but not 1 μg/ml) significantly reduced the increases in outputs of PGF_2α, PGE₂ and 6-keto-PGF_1α induced by A23187 from the Day 15 guinea-pig uterus, without affecting basal PG outputs. The increase in uterine tone induced by A23187 in the Day 15 guinea-pig uterus was reduced by 20–50% by oestradiol (10 μg/ml). The addition of oestradiol (10 μg/ml) and progesterone together (10 gmg/ml) produced the same effects on the Day 15 guinea-pig uterus as oestradiol alone. Oestradiol (10 μg/ml) also reduced the A23187-induced increases in PG output from the Day 7 guinea-pig uterus, but did not reduce the increase in uterine tone. Oestradiol (10 gmg/ml) reduced the increases in outputs of PGF_2α, PGE₂ and 6-keto-PGF_1α induced by exogenous arachidonic acid from the Day 7 and Day 15 guinea-pig uterus. Previous studies have shown that oestradiol is not a cyclo-oxygenase inhibitor. The present findings suggest that oestradiol, at a relatively high concentration, may interfere with the access of arachidonic acid to the cyclo-oxygenase enzyme. This action of oestradiol may explain its anti-luteolytic action when administered to guinea-pigs in large doses after Day 9 of the cycle.     

Biosynthesis of prostaglandins and thromboxane B2 by fetal lung homogenates

The conversion of arachidonic acid to prostaglandins (PG's) and thromboxane B₂ (TXB₂) was investigated in homogenates from fetal and adult bovine and rabbit lungs. Adult bovine lungs were very active in converting arachidonic acid (100 μg/g tissue) to both PGE₂ (10.7 μg/g tissue) and TXB₂ (6.2 μ/g tissue). Smaller amounts of PGF_2α (0.9 μ/g) and 6-oxoPGF_1α were formed. Homogenates from fetal calf lungs during the third trimester of pregnancy were quite active in converting arachidonic acid to PGE₂, but formed very little TXB₂, PGF_2α or 6-oxoPGF_1α. Homogenates from rabbit lungs converted arachidonic acid (100 μg/g) mainly to PGE₂, both before and after birth. The amount of PGE₂ formed increased during gestation to a maximum of about 6 μg/g tissue at 28 days of gestation. It then decreased to a minimum (1.5 μg/g) which was observed 8 days after birth, followed by an increase to about 4 μg/g in older rabbits.     

Is prostaglandin F2α involved in the increased myometrial contractility of primary dysmenorrhoea?

The concentrations of prostaglandin F₂α (PGF₂α) and E₂ (PGE₂) in menstrual fluid collected daily from 13 women with primary dysmenorrhoea and 11 matched controls, were compared with the pattern of uterine contractility during the hour following the menstrual fluid collection. The intra-uterine pressure (IUP) was measured using a micro-transducer catheter and the tracings analysed.On Day 2 the concentration of PGF₂α correlated with the peak area, but not with amplitude, duration or rate of contraction. These findings add additional support to the hypothesis that increased production of PGF₂α could contribute to the increased uterine contractility in primary dysmenorrhoea.     

Determination of menstrual prostaglandin levels in non-dysmenorrheic and dysmenorrheic subjects

We have developed a method which can measure the menstrual prostaglandin (PG) activity in a single tampon specimen by bioassays. This method makes it possible to monitor the menstrual PG activity continuously during menstruation. Using this technique, we determined the menstrual PG patterns of two normal non-dysmenorrheic subjects, one subject on oral contraceptives (OC) and one subject with moderate to severe dysmenorrhea. Two to four cycles were studied per subject. We observed three menstrual patterns among the four subjects studied. Compared to the two normal controls, the subject on OC had a significantly lower menstrual fluid total and menstrual PG activity. The mean values ± S.E. per menstrual period were 33.4 g ± 1.5 vs 21.5 g ± 2.0 and 28.6 μg (PGF_2α equivalent) ± 1.5 vs 11.3 μg ± 4.2 respectively (control vs OC). The dysmenorrheic subject had a menstrual fluid total of 37.0 g ± 1.9 similar to the two normal controls. Her menstrual PG activity (49.8 μg ± 7.7), however, was nearly two times higher than the normal controls. In one cycle studied, the dysmenorrheic subject was treated with a PG synthetase inhibitor, ibuprofen (Motrin). Remarkable relief was achieved. The alleviation of symptoms was accompanied by a concomitant marked reduction in the menstrual PG activity.     

Antagonistic Action of Aerosols of Prostaglandins F2α and E2 on Bronchial Muscle Tone in Man

Experiments were carried out in healthy male volunteers to investigate the effect of the inhalation of prostaglandin F₂α (PGF₂α) on airways resistance and the influence of the subsequent inhalation of prostaglandin E₂ (PGE₂). Airways resistance, which reflects the tone of smooth muscle in the larger airways in man, was measured by total body plethysmography.The inhalation of PGF₂α (40-60 μg) caused an increase in airways resistance in all subjects. Both PGE₂ (55 μg) and isoprenaline (550 μg) given by metered aerosol promptly reversed the bronchoconstriction induced by PGF₂α, but isoprenaline was more effective in this respect.A role for these prostaglandins in the control of bronchial muscle tone is discussed.     

Prostaglandin E1 inhibits the pulmonary vascular pressor response to hypoxia and prostaglandin F2α

In the anesthetised dog an infusion of exogenous prostaglandin E₁ (100μG/min) inhibits the pulmonary vascular pressor response to hypoxia. Both 25 and 100 μG/min PGE₁ can reduce the transient pulmonary hypertension caused by a bolus of prostaglandin F_2α. This suggests that hypoxia and PGF₂α may share a final common pathway in producing pulmonary vasoconstriction. These results may help to explain the mechanism by which endotoxin inhibits the pulmonary vascular response to hypoxia. This effect is probably achieved by stimulating the production of an endogenous dilator prostaglandin. Exogenous PGE₁ can mimic this effect.     

Different responses to prostaglandin F2α and E2 in human extra- and intramyometrial arteries

Tubal segments of the ascending uterine arteries and of intramyometrial arteries were obtained from 18 women who underwent hysterectomy at various phases of the menstrual cycle. Ring preparations of the vessels were mounted in organ baths and isometric tension was recorded. In extramyometrial arteries (outer diameter 2–3 mm) prostaglandin (PG) F_2α most potently, but also PGE₂ caused concentration-related contractions. In contrast, the contractant effects of both PGs on intramyometrial arteries (outer diameter 0.5–0.6 mm) were negligible. Both extra- and intramyometrial vessels were relaxed to a moderate degree (10–25%) by low concentrations of PGF_2α and PGE₂. No significant differences between the responses to vasopressin and noradrenaline were found between the vessel preparations. Thus human uterine arteries seem to change their responses to PGF_2α and PGE₂ as they enter the myometrium and decrease in diameter, and the results raise doubt about the view that direct vasoconstrictor effects of these PGs contribute to the regulation of myometrial blood flow. Such effects of vasopressin and noradrenaline cannot be excluded.     

Macrophage prostaglandin E2 and oxidative responses to endotoxin during immunosuppression associated with anaesthesia and transfusion

The widespread use of blood transfusion in major surgical procedures has led to concern about the immunosuppressive effect of transfusion on patients with underlying malignancy. Transfusion may also suppress the host response to infection. The cellular mechanisms of transfusion-associated immunosuppression may involve macrophage prostaglandin E₂ (PGE₂) in modulating the host response to cancer and infection. We previously observed that the transfusion of blood increased PGE₂ production by unstimulated macrophages. To investigate this PGE₂ associated immunosuppression, we studied the effect of transfusion of rats using a physiological stimulus of macrophage PGE₂ production, bacterial endotoxin. In the same macrophages, we analysed intracellular oxidative activity. Both allogeneic and syngeneic blood transfusion were associated with increased PGE₂ release by macrophages. This stimulation of PGE₂ increased with duration of storage of blood. A similar effect of serum indicated that a humoral factor was involved. Endotoxin (50 ng/ml–500 μg/ml) stimulated PGE₂ production in all transfused subjects. The lowest endotoxin concentration gave proportionately the greatest stimulation. Oxidative activity was down-regulated in macrophages of transfused rats, supporting an immunosuppressive role of PGE₂ within the macrophage. An effect of surgery on the oxidative response was also detected.     

Fetal-maternal secretion of prostaglandins in the cow

A study was conducted to measure the blood plasma concentrations of prostaglandin F₂α (PGF₂α), 13,14-dihydro-15-keto-prostaglandin F (PGFM), 6-keto-prostaglandin F₁α (6-keto), prostaglandin E₂ (PGE₂), and thromboxane B₂ (TBX₂) in the ovarian vein, uterine artery, uterine vein, umbilical artery and umbilical vein in 24 cows from days 80 to 260 of pregnancy. Blood was collected during surgery and all prostaglandins were measured using specific radioimmunoassay procedures. Results indicate that PGF₂α blood levels are higher in the umbilical vessels and uterine vein than in the ovarian vein and uterine artery. PGFM and PGE₂ showed a trend towards higher values in the umbilical than in the maternal vessels, but the levels of 6-keto and TBX₂ were not different among the vessels studied. No differences across time couls be observed in any of the prostaglandins measured, partly due to the great variability in blood levels among animals during the same stage of pregnancy.     

Prostaglandin E inhibition of mitogen stimulation in patients with multiple sclerosis

Kirbey et al have reported that leukocyte function from patients with multiple sclerosis is not suppressed by PGE₂, as are normal leukocytes. We examined the ability of PGE₂ (0.01–0.5 μg/ml) to suppress Phytohemagglutinin induced ³H-thymidine incorporation in peripheral blood lymphocytes from multiple sclerosis patients and normals. There was no difference in sensitivity between the two groups. There was also no difference in activity of the prostaglandin producing suppressor cell between the multiple sclerosis patients and controls.