The effects of prostaglandins E 2 and F 2 alpha administered by different routes on uterine activity and the cardiovascular system in pregnant and non-pregnant women

Paracetamol - An old drug with new mechanisms of action

Paracetamol (acetaminophen) is the most commonly used over-the-counter (OTC) drug in the world. Despite its popularity and use for many years, the safety of its application and its mechanism of action are still unclear. Currently, it is believed that paracetamol is a multidirectional drug and at least several metabolic pathways are involved in its analgesic and antipyretic action. The mechanism of paracetamol action consists in inhibition of cyclooxygenases (COX-1, COX-2, and COX-3) and involvement in the endocannabinoid system and serotonergic pathways. Additionally, paracetamol influences transient receptor potential (TRP) channels and voltage-gated Kv7 potassium channels and inhibits T-type Cav3.2 calcium channels. It also exerts an impact on L-arginine in the nitric oxide (NO) synthesis pathway. However, not all of these effects have been clearly confirmed. Therefore, the aim of our paper was to summarize the current state of knowledge of the mechanism of paracetamol action with special attention to its safety concerns.

Long chain polyunsaturated fatty acids alter oxytocin signaling and receptor density in cultured pregnant human myometrial smooth muscle cells

Epidemiological studies and interventional clinical trials indicate that consumption of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) such as docosahexaenoic acid (DHA) lengthen gestational duration. Although the mechanisms are not well understood, prostaglandins (PG) of the 2-series are known to play a role in the initiation and progress of labor. In animal studies, modest DHA provision has been shown to reduce placental and uterine PGE(2) and PGF(2α), matrix metalloproteinase (MMP)-2 and MMP-9 expression, and placental collagenase activity. However, modulation of PG biosynthesis may not account for all the effects of LC n-3 PUFAs in labor. We investigated one potential PG-independent mechanism of LC PUFA action using cultured pregnant human myometrial smooth muscle cells. Our goal was to characterize the effect of LC PUFA treatment on oxytocin signaling, a potent uterotonic hormone involved in labor. The addition of 10 µM-100 µM DHA or arachidonic acid (AA) to the culture media for 48 h resulted in dose dependent enrichment of these fatty acids in membrane lipid. DHA and AA significantly inhibited phosphatidylinositol turnover and [Ca(2+)](i) mobilization with oxytocin stimulation compared to bovine serum albumin control and equimolar oleic acid. DHA and AA significantly reduced oxytocin receptor membrane concentration without altering binding affinity or rate of receptor internalization. These findings demonstrate a role for LC n-3 PUFAs in regulation of oxytocin signaling and provide new insight into additional mechanisms pertaining to reports of dietary fish and fish oil consumption prolonging gestation.

Papaya (Carica papaya) consumption is unsafe in pregnancy: fact or fable? Scientific evaluation of a common belief in some parts of Asia using a rat model

Using controlled in vivo and in vitro pharmacological methods, we evaluated the safety of papaya (Carica papaya) consumption in pregnancy with reference to its common avoidance during pregnancy in some parts of Asia. Ripe papaya (Carica papaya L. (Caricaecae) blend (500 ml/l water) was freely given to four groups of Sprague-Dawley rats at different stages of gestation (days 1–5, 6–11, 12–17 and 1–20). The control group received water. The effect of ripe papaya juice and crude papaya latex on pregnant and non-pregnant rats' uteri was also evaluated using standard isolated-organ-bath methods. The daily volumes (ml) of ripe papaya blend consumed by the treated group were significantly (P<0·05) more than water consumed by the control (control 40·3 (<FONT SIZE="-2">SD</FONT> 11·6) v. treated 64 (SD 19·0)). There was no significant difference in the number of implantation sites and viable fetuses in the rats given ripe papaya relative to the control. No sign of fetal or maternal toxicity was observed in all the groups. In the in vitro study, ripe papaya juice (0·1–0·8 ml) did not show any significant contractile effect on uterine smooth muscles isolated from pregnant and non-pregnant rats; conversely, crude papaya latex (0·1–3·2 mg/ml) induced spasmodic contraction of the uterine muscles similar to oxytocin (1–64 mU/ml) and prostaglandin F2α (0·028–1·81 μM). The response of the isolated rat uterine smooth muscles to 0·2 mg crude papaya latex/ml was comparable to 0·23 μM prostaglandin F2α and 32 mU oxytocin/ml. In the 18–19 d pregnant rat uterus, the contractile effect of crude papaya latex was characterized by tetanic spasms. The results of the present study suggest that normal consumption of ripe papaya during pregnancy may not pose any significant danger. However, the unripe or semi-ripe papaya (which contains high concentration of the latex that produces marked uterine contractions) could be unsafe in pregnancy. Though evaluation of potentially toxic agents often relies on animal experimental results to predict risk in man, further studies will be necessary to ascertain the ultimate risk of unripe papaya–semi-ripe papaya consumption during pregnancy in man.

A retrospective study of 11 pregnant women with thermal injuries

Out of 917 burn victims admitted to the Burn Unit of Ankara Numune Hospital between 1986 and 1994, the records of 11 pregnant patients were scrutinized retrospectively. All patients were classified by using the rule of 9's. Two maternal deaths (18%) occurred in patients with burns involving more than 50% of the skin surface area and there were four fetal deaths (36%) which occurred less than 72 h after the burns. These findings support the views that maternal and perinatal outcome is related to the burn severity (surface area + depth), to the presence or absence of complications and to the gestational age of the fetus. In view of the high perinatal mortality, in any patient with extensive burns who is more than 32 weeks pregnant, the fetus should be delivered soon after admission.

Modulation of human myometrial PGE2 receptor by GTP characterization of receptor subtype

We studied PGE2 specific binding sites in human myometrial microsomes prepared from uterine specimens obtained by hysterectomy (women between 38 and 55 years of age). Competition experiments showed that the potency order for various prostaglandins (PGs) was: PGE2 > or = PGE1 >> PGF2 alpha > Iloprost > or = Carbacyclin >> ZK 110841 (PDG2 analogue). These relative affinities indicated that the receptor was of the EP type. In kinetic experiments GTP, GppNHp and GTP gamma S increased the rate of PGE2 binding (steady state was reached more rapidly in the presence of nucleotides) but maximal specific binding was not significantly different. Complete dissociation could not be obtained, even in the presence of GTP. Only 50% of maximal binding was readily dissociable. The dissociation rate was 4.56.10(-4) sec-1 (half time of about 660 sec) and in the presence of GTP analogues it was slightly increased (k-1 = 7.16 10(-4) sec-1, half time 420 sec.). Scatchard analysis of saturation curves showed an increase in ligand receptor affinity in the presence of GTP or nucleotide analogues: the Kd shifted from 9.66 +/- 2.8.10(-9) M to 4.96 +/- 1.25.10(-9) M, but the number of binding sites did not change significantly (310 +/- 37 to 350 +/- 17 fmol/mgP). The effect of GTP was observed at a concentration of 5.10(-4)M. GppNHp and GTP gamma S were effective at 1.10(-5) M. Pretreatment of myometrial membranes with pertussis or cholera toxins had no effect on PGE2 binding to membrane sites. Our conclusion is that GTP induced conversion of a population of low affinity sites into a population of higher affinity sites. This effect of guanine nucleotides was described in adipocytes and kidney medulla. Competition studies with PGE2 analogues (sulprostone, 17-phenyl-omega-trinor PGE2, M&B 28,767, misoprostol, butaprost) showed that this receptor mediates a contractile response and is probably an EP3 subtype.

Comparison of two dosages of prostaglandin F2a on canine uterine motility

The effect of 50 ug/kg prostaglandin F2a (PGF2a) was compared with 250 ug/kg PGF2a on uterine motility in the diestrous female. Microtipped pressure transducers were surgically implanted in the uteri of 6 females at 30 days diestrus and in 6 females at 60 days diestrus. Uterine responses to intravenous PGF2a (5 ug/kg), oxytocin (0.05 USP units/kg), and intramuscular PGF2a (50 ug/kg and 250 ug/kg) were measured in the awake females on Days 1 and 2 after implantation. There was no significant difference in the increase in intrauterine pressure produced by 50 ug/kg of PGF2a compared with 250 ug/kg of PGF2a. The longest duration of the effect occurred when 250 ug/kg of PGF2a were given. Side effects were also documented. Significantly more vomiting occurred when 250 ug/kg PGF2a were given than when 50 ug/kg PGF2a were administered. The only advantage to using a higher dosage of PGF2a appears to be the longer duration of motility.

In vitro characterization of prostanoid EP-receptors in the non-pregnant human myometrium

1. Prostaglandin receptors of the PGE type have been characterized in the non-pregnant human myometrium in vitro according to the scheme of Coleman et al. (1984) by use of the agonists PGE2, sulprostone, rioprostil, AY23626, butaprost, misoprostol, 16,16-dimethylprostaglandin E2, enprostil and iloprost, and, the antagonist AH6809. 2. All prostanoids tested were active in non-pregnant human myometrium either as stimulators and/or inhibitors of spontaneous activity or both. Biphasic responses to PGE2 indicate that at least two receptor types of the EP-receptor exist, one mediating relaxation and the other mediating contraction. 3. Further evidence for the EP-receptor mediating excitation and relaxation was provided by the action of the EP2-/EP3-receptor selective prostanoids rioprostil, AY23626 and misoprostol, and the EP1-/EP2-receptor selective agonist 16,16-dimethylprostaglandin E2. 4. Butaprost, an EP2-receptor selective agonist, produced potent inhibition of spontaneous activity in the tissue which was generally longer-lasting than that evoked by the natural prostanoid PGE2. 5. The EP1-/EP3-receptor selective agonist sulprostone and the EP3-receptor agonist enprostil produced potent contractile responses supporting the presence of contractile EP3-receptors in the non-pregnant human myometrium in vitro. 6. The EP1-/IP-receptor selective agonist, iloprost, produced mixed responses in non-pregnant human myometrium. The contractile response was inhibited by the EP1-receptor antagonist AH6809. However, responses to the EP1-/EP3-receptor selective agonist sulprostone were unaffected by AH6809 which may indicate that only a small population of EP1-receptors is present. 7. Therefore it would seem that a heterogeneous population of EP-receptors is present in the non-pregnant human myometrium.

Prostaglandin E receptors in cardiac sarcolemma. Identification and coupling to adenylate cyclase

Purified cardiac sarcolemmal membrane vesicles were used to determine if specific prostaglandin (PG) receptors are present on the myocyte. Two binding sites for PGE2 were identified in isolated bovine sarcolemmal membranes: a high-affinity site with a dissociation constant (Kd) of 0.32 nM and a maximum binding (Bmax) of 376 fmol/mg of protein and a lower-affinity site with a Kd of 3.41 nM and a Bmax of 2,112 fmol/mg of protein. In competition experiments, unlabeled PGE1 displaced [3H]PGE2 from its membrane receptor at concentrations similar to those of unlabeled PGE2. Both PGF2 alpha and PGD2 displaced [3H]PGE2 from the membrane, but only at high concentrations (greater than 10(-6) M and greater than 10(-5)M, respectively). Digestion of sarcolemmal membrane with trypsin resulted in a threefold decrease in specific [3H]PGE2 binding. Phosphorylation of the membrane with protein kinase A also decreased specific [3H]PGE2 binding. At concentrations of PGE2 that occupy the high-affinity site, sarcolemmal adenylate cyclase activity was inhibited in the presence of 5'-guanylylimidodiphosphate [Gpp(NH)p]. We conclude that the isolated cardiac sarcolemmal membrane contains a high-affinity binding site for PGE2 that is functionally coupled to adenylate cyclase. The binding site is stereospecific and probably recognizes the 9-keto,11-hydroxyl portion of the ring structure of these prostaglandins.

The concentrations of prostaglandins in endometrium during the menstrual cycle in women with measured menstrual blood loss

The concentrations of PGF2 alpha, PGE2 and 6-oxo-PGF1 alpha were measured in human uterine tissues during the menstrual cycle. The concentrations of all PGs in endometrium were greater than in myometrium. PGF2 alpha, which was found in the greatest concentrations, was high in the mid-secretory phase in both endometrium and myometrium. The concentration of PGE2 did not vary during the menstrual cycle in either tissue. The biosynthetic capacity of endometrium to produce both PGF2 alpha and PGE2 was significantly greater in the mid than the late secretory phase in the presence of exogenous arachidonic acid. Also, in spite of low endogenous concentrations, both endometrium and myometrium were able to produce significant amounts of 6-oxo-PGF1 alpha during a 30 minute incubation. The possible significance of this late secretory decline in the capacity of the endometrium to produce PGF2 alpha and PGE2 is discussed.

A clinical trial of prostaglandin E2 to increase erythropoiesis in anemia of end stage renal disease. A preliminary report

Prostaglandin E2 is known to stimulate erythropoiesis by different mechanisms. A clinical trial of prostaglandin E2 to stimulate erythropoiesis in four patients with anemia of end stage renal disease resulted in an increment in peripheral blood Burst Forming Units-Erythroid (BFU-E). This increase in erythroid progenitors returned to baseline with cessation of therapy. A significant increase in serum erythropoietin (EPO) activity was demonstrated in one patient and was noticeable in another. Side effects mainly consisted of local pain at the site of the infusion and vomiting.

Primary dysmenorrhoea: the importance of both prostaglandins E2 and F2 alpha

Menstrual fluid was collected in a contraceptive diaphragm from 16 women with primary dysmenorrhoea and 12 matched control subjects without dysmenorrhoea. Prostaglandins F2 alpha (PGF2 alpha), E2 (PGE2) and 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha) were extracted and measured using gas-chromatography: mass spectrometry (GC:MS). The concentrations of both PGF2 alpha and PGE2 were higher on days 1 and 2 in the dysmenorrhoea group than in the control group and the concentration of PGF2 alpha was higher on day 1 than on day 2 in the dysmenorrhoea group. The concentrations of 6-oxo-PGF1 alpha (the stable metabolite of PGI2) were low in both groups. These results confirm suggestions that PGF2 alpha is important in the aetiology of dysmenorrhoea and also indicate that PGE2 may be involved.

Evaluation of antiarrhythmic activity of prostaglandin F2 alpha in man

Since prostaglandin (PG) F2 alpha had been shown to act anti-arrhythmically in various animal models and also in preliminary investigations in man, further evaluation of this effect was made in 30 patients with cardiac extrasystoles and in 2 patients with tachycardias. PGF2 alpha was infused intravenously at individually adapted consecutive rates from 5 to 100 micrograms/min each for at least 5 min. In the incidence of extrasystoles a mean maximum decrease of 41% (P less than 0.001) was obtained. One patient showed repeated short interruptions of a ventricular tachycardia. A dose-dependent significant rise in blood pressure and no significant influences on heart rate, PQ interval and QRS interval of the ECG were found. It is concluded that PGF2 alpha has probably no practical importance for the therapy of cardiac arrhythmias.

Is prostaglandin F2 alpha involved in the increased myometrial contractility of primary dysmenorrhoea?

The concentrations of prostaglandin F2 alpha (PGF2 alpha) 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 PGF2 alpha 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 PGF2 alpha could contribute to the increased uterine contractility in primary dysmenorrhoea.

A major burn in early pregnancy with maternal survival and pregnancy progressing to term

A case is presented of a 65% burn occurring in early pregnancy with maternal survival and a pregnancy progressing to term. This would appear to be only the third such case recorded in the literature. Maternal and foetal prognosis are discussed and the guidelines proposed by Stage (1973) for the management of pregnancy complicated by a major burn are restated.

Intramuscular administration of 15-methyl prostaglandin F2alpha in mid-trimester termination of pregnancy

15-methyl prostaglandin F2 alpha was administered by intramuscular injection to thirty patients to terminate pregnancy in the mid-trimester. Termination was considered successful if this occurred within 24 hours and this was so in twenty-seven cases (90%). There were no serious complications. prochlorperazine mesylate and diphenoxylate hydrochloride reduced the incidence and severity of vomiting and diarrhoea.

Effects of induction of labor on the neurophysiologic functioning of newborn infants

Neurophysiologic responses of newborn infants delivered after normal onset of labor are compared with those of newborn infants whose mothers had labor induced with oxytocin or prostaglandin F2 alpha. No differences in brain activity or heart rate were detected between groups in terms of frequency of response to auditory, visual, tactile, or olfactory stimulation. Significant differences were found for resting brain activity defined in terms of autoregressive spectral estimates or coefficients. The largest differences were between the groups with normal onset of labor and prostaglandin F2 alpha.

Intramuscular 16-phenoxy PGE2 ester for pregnancy termination

A new PGE2 derivative (16-phenoxy PGE2 methyl sulfonylamide sulprostone) was administered by the i.m. route to 48 women pregnancy in any of the three trimesters. The indications for pregnancy interruption were either serious medical problems in intact pregnancies (21 cases) or due to fetal death in utero (27 cases). Single doses of 500 micrograms were repeated every 4 hours in the former group or every 6 hours in the latter category for a maximum period of 24 hours. The treatment was successful in 81% of intact pregnancies and in 92.6% of fetal death cases with an overall mean induction interval of 12.9 hours. More than half the subjects did not experience any side effects apart from mild or moderate uterine colics. An overall mean of 1.4 episodes of vomiting or diarrhoea per induction trial was quite acceptable from the clinical point of view. The absence of serious complications in the group of critically sick women speaks in favor of the relative safety of the drug.

The possible mode of action of prostaglandins: XIV. Evidence of an involvement of progesterone in the initiation of prostaglandin F2a-induced premature labor in rats

Prostaglandin F2a (PGF2a) at a dose of 2 mg/kg (sc) on day 18 of pregnancy induced premature emptying of gravid uteri by day 21 in the rat. Bilateral spaying or luteectomy on day 18 of pregnancy induced a refractoriness to respond to the abortifacient action of PGF2a. Injection of progesterone in the spayed or luteectomized pregnant rats, however, restored the sensitivity of the surgically manipulated animals to PGF2a. Premature parturition resulted in all of the animals so far tested. The importance of progesterone in terms of the abortifacient action of PGF2a is discussed.

New concepts in dysmenorrhea

The etiology of primary dysmenorrhea, which is the most common gynecologic complaint and cause of lost working hours, remains obscure but merits careful scientific investigation. Recent studies suggest that increased endometrial prostaglandin production and release may be responsible for dysmenorrhea. Prostaglandins cause myometrial contractility that, if excessive, leads to uterine ischemia and pain. This hypothesis has led to clinical trials of antiprostaglandin agents such as indomethacin and fenamates, which inhibit the synthesis of prostaglandin through the prostaglandin synthetase system as well as antagonize their action at the cell receptor level. The good response of dysmenorrhea to other conventional forms of therapy such as oral contraceptives and dilatation of the cervix can be partly explained on the basis of a reduced level of prostaglandins in the menstrual fluid with such therapy. There is a definite need for further evaluation of the antiprostaglandin compounds in the treatment of dysmenorrhea so that sound formulations can be evolved for the elimination of this incapacitating disorder.

Reduced uterine response to PGF2alpha under oral contraceptives

The effect of prostaglandin F2alpha (PGF2alpha) on the nonpregnant human uterus was evaluated in 35 patients. The compound was administered both by intra-uterine and intravenous routes. Two groups of volunteers were studied;fifteen cases who were under oral contraceptives and twenty women with normal ovulatory cycles. The uterus under the influence of oral contraceptives showed a reduced response to local and systemic administration of PGF2alpha at all phases of the menstrual cycle. The implications of these findings in certain physiological and pathological conditions related to reproduction are discussed.

Aberrant uterine response to prostaglandin E2 as a possible etiologic factor in functional infertility

The clinical entity of functional infertility still remains unexplained and largely lacking a line of proper management. The uterine response to prostaglandin E2 (PGE2) and prostaglandin F2alpha (administered by intravenous and intrauterine routes) was evaluated during different phases of the menstrual cycle in five functionally infertile women. The results (quantitative and qualitative) were compared with those elicited among 20 fertile women. There were no apparent differences between the two groups with respect to either compound (systemic or local) when given during the proliferative or luteal phase of the cycle. However, at midcycle, about the time of ovulation (days 13 to 18), there was a salient deviation in the type of response following local instillation of PGE2; in the normal fertile group there was a definite inhibition of motility, while uteri in the functionally infertile group showed marked stimulation. The possible role of this aberrant uterine response in the etiology of functional infertility is discussed.

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.

Uterine contractility and regional blood flow responses to oxytocin and prostaglandin E2 in pregnant rhesus monkeys

The effects of oxytocin and prostaglandin E2 (PGE2) infusions on regional blood flow (measured by radioactive microspheres) and myometrial contractility were studied in 18 pregnant rhesus monkeys near term. We observed no significant differences between PGE2 and oxytocin in cardiac output, hemodynamics, or uterine activity. Their effects on the regional distribution of systemic blood flow were similar although the gastrointestinal tract received an increased percentage of cardiac output after PGE2. A relative placental ischemia, together with a myometrial hyperemia, was observed during labor. Uterine contraction produced a large reduction (average 73 per cent) in placental blood flow whereas myometrial blood flow was maintained or sometimes increased. A significant negative correlation was observed between intra-amniotic pressure and placental blood flow. During uterine relaxation, placental flow partially recovered whereas myometrial flow nearly doubled the prelabor values. We conclude that (1) in the dose ranges studied, oxytocin and PGE2 produce similar effects on myometrial contractility and uteroplacental blood flow, and (2) the vascular beds of the placenta and myometrium respond differently to labor of moderate intensity.

Myocardial infarction and rheumatic heart disease in pregnancy. Case report

Myocardial infarction is a rare complication of pregnancy, only 45 proven cases having been reported. In only one patient was rheumatic heart disease an associated factor (Goldberger and Pokress, 1950).

The relaxant property of local prostaglandin E-2 on the non-pregnant uterus - a cyclic triphasic response

The response of the non-pregnant human uterus to intravenous (i.v.) injections and intra-uterine instillation of various doses of prostaglandin E-2 (PGE-2) was evaluated at the different phases of the menstrual cycle in 13 fertile regularly menstruating women who were neither lactating nor using any hormonal therapy. Uterine contractility was recorded by the microballoon technique in at least three sessions(proliferative, mid-cycle and secretory) in a single cycle with endometrial biopsy performed immediately following the last session to ascertain that the particular cycle was an ovulatory one. Single i.v. injections of PGE-I had a consistent stimulatory effect on the contractility throughout the cycle with a tendency towards a decreased uterine response at mid-cycle and luteal phase as compared to the proliferative part of the cycle. Intra-uterine instillation of the compound induced a peculiar and interesting type of response. In the proliferative and secretory phases of the cycle the response was one of stimulation; being more pronounced in the former period. However, around ovulation time, the local administration induced an evident uterine relaxation in most cases without any instance of stimulation. The possible implication of this triphasic response behaviour on the non-pregnant uterus within certain physiological events and pathological conditions is discussed.

The synthesis of prostaglandin F by human endometrium in organ culture

Slices of human endometrium obtained from hysterectomy specimens were cultured for 48 hours in an organ culture medium supplemented with ethanol (control, vehicle), 17-beta-estradiol (.5 mug/ml), or progesterone (.5 mug/ml). Uncultured endometrial tissue, cultured tissues, and the media were assayed for prostaglandin F (PGF) by a radioimmunoassay technique. Hematoxylin and eosin and periodic acid-Schiff stain histologic controls were done on all tissues. The concentrations of PGF in picograms/milligram, corrected for percent recovery, in the differently treated tissues were: preculture 298; culture control 2210; estrogen-treated 2680; progesterone-treated 1260. All differences except those between estrogen and control (p greater than .10) and progesterone and control (p less than .10) are significant at the p = .02 level or better. Progesterone appears to inhibit PGF synthesis which occurs during in vitro culture of human endometrium; estrogen tended to increase PGF synthesis in this system.

The effect of locally administered PGF2alpha on the contractility of the nonpregnant human uterus

The effect of locally administered prostaglandin F2alpha 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 MUG PGF2alpha 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 PGF2alpha plays an important physiological role in the cyclical regulation of uterine motility during the human menstrual cycle.