Oxytocin augmentation of second-trimester abortion: safe or hazardous?

The role of oxytocin in augmenting the uterine activity of second-trimester instillation abortions is controversial. To evaluate the efficacy and safety of oxytocin augmentation, we studied 10,013 women who underwent hypertonic saline instillation procedures and 1,241 women who underwent prostaglandin F2a (PGF2a) instillation procedures in the United States in the period 1971 through 1975. Data were obtained through the Joint Program for the Study of Abortion under the auspices of the Center for Disease Control, a multi-center, prospective, cohort study. We found that concurrent administration of oxytocin was associated with a significantly shorter instillation-to-abortion time for hypertonic saline, but with a significantly longer time for PGF2a. For hypertonic saline, use of concurrent oxytocin did not affect either the success rate or the major complication rate; however, it did not affect the specific type of complication that occurred. For PGF2a, use of concurrent oxytocin was associated with a lower success rate and a higher major complication rate than when PGF2a was used alone; however, the relatively small number of observations and limitations in our study design may have affected our results. When we compared the 2 main abortifacients, even when we controlled for concurrent oxytocin augmentation, unaugmented PGF2a had higher major complication rates than hypertonic saline.

Effects of prostaglandin-F2 alpha and a plant protein "Trichosanthin", on 10-day pregnant rabbits

The effect of Trichosanthin (TCS), a protein obtained from the roots of Trichosanthis kirilowii, alone or in combination with prostaglandin-F2 alpha (PGF2 alpha; Tromethamine salt) on the termination of pregnancy in rabbits was investigated. Intraperitoneal injection of 1 or 2 mg TCS/10-day pregnant rabbits neither altered the serum progesterone (delta 4P) level nor interrupted pregnancy. Doses of 0.5 or 0.25 mg PGF2 alpha incorporated in a Silastic-PVP tube and inserted intravaginally, terminated pregnancy within 72 h of treatment in 75 and 16% of the treated does, respectively. By contrast, does treated on day-10 of pregnancy with a combination of a non-effective dose of TCS (1 mg) and a sub-effective dose of PGF2 alpha (0.25 mg) terminated pregnancy in all the treated animals as no live embryos were found within 3 days of treatment. Pregnancy interruption was associated with a significant reduction of serum delta 4P and delta 4P/20 alpha-dihydroprogesterone (20 alpha-DHP) ratio. The present study indicates that TCS and PGF2 alpha act synergistically, rendering the termination of 10-day pregnancy possible in the rabbit. It was also noted that pregnancy cannot be maintained when the serum delta 4 P level drops below 4 ng/ml and delta 4P/20 alpha-DHP falls lower than 0.6 in the 10-day pregnant rabbit.

[Changes of the contraction of the circular and longitudinal muscles of pregnant rat myometrium during pregnancy (author's transl)]

The different reactions caused by 4 drugs (terbutaline sulphate, noradrenaline, PGF2 alpha and oxytocin) and Ca on the longitudinal and circular muscles of a pregnant rat myometrium as well as their electrical activity and the degree of their co-ordinated contractions during pregnancy were studied in vitro. The results were as follows; 1. The circular muscle showed plateau potential in the middle, but spike potential became dominant in the late stage. The longitudinal muscle, however, showed spike potential throughout. 2. Well co-ordinated contraction between 1) the neighboring longitudinal muscles, 2) the neighboring circular muscles, and 3) the longitudinal and circular muscles were evident in the late stage. 3. The circular muscle was stimulated by noradrenaline in the middle stage, but inhibited by it in the late stage, whereas the longitudinal muscle was inhibited throughout. 4. The circular muscle developed high sensitivity to terbutaline sulphate in the late stage, whereas the longitudinal muscle showed constant sensitivity throughout. 5. PGF2 alpha failed to cause contracture of the circular muscle in the late stage. 6. The high resistance of the circular muscle to low Ca in the middle stage weakened in the late stage, whereas the longitudinal muscle resistance was low in both stages. In conclusion, in the final stage of pregnancy, the action of the circular muscles resembles that of the longitudinal ones, however, the contracture of the circular muscles is difficult to notice. For the purpose of the expulsion of the uterine contents, the longitudinal muscle may play main role. While the longitudinal muscle is in the contracture state, the circular muscle may show repeated coordinated contractions, thereby assisting the expulsion of the contents.

Regulation of the estrous cycle in domestic animals-- a review

Neuroendocrine and endocrine factors involved in the regulation of reproductive cycles in domestic animals are discussed. Although research data from many species are considered, emphasis is placed on their relevance for the cow, sow, ewe and, to a lesser extent, the mare. Literature cited is not designed to be complete, but rather to be representative of the large volume of material which has been written on the subject.Gonadotropin-releasing hormone is synthesized and secreted in response to various exteroceptive stimuli, but both its release and its effects on the anterior pituitary are modified by feedback of target gland hormones. A modulating role for nonsteroidal regulators such as inhibin has yet to be proven. Prostaglandins are important for corpus luteum regression and ovulation. The relative roles of the gonadotropins and the above substances in hypothalamic, adenohypophyseal and ovarian function are considered. General mention is made of mechanisms of hormonal action.

[Effect of prostaglandin F2 alpha on the acute toxicity of cholinergic drugs in mice]

Studies on white mice of acute toxicity of cholinergic drugs (carbachol, physostigmine, pilocarpine) intraperitoneally made it possible to ascertain the magnitudes of DL50 as follows: 2.5 mg/kg for carbachol, 0.644 mg/kg for physostigmine and 150 mg/kg for pilocarpine. Intraperitoneal administration of prostaglandins F2 alpha (10 and 25 mg/kg) 15 min before carbachol, physostigmine and pilocarpine increased the toxicity of the drugs and considerably lowered their DL50, while the administration of the same doses of prostaglandins F2 alpha in control mice did not enhance side effects. The animals' survival after 24 hours elapsed was equal to 100%.

The effect of prostaglandin F2 alpha and oxytocin on bovine myometrium in vitro

Uterine strips were collected from cows during the follicular and the luteal phases as well as from cows with ovarian cysts. The strips were mounted in organ baths and the motility was recorded by a polygraph. After the spontaneous motility of the strips had reached a steady state the test substances PGF2 alpha and oxytocin were added to the bath at three different concentrations. Frequency, amplitude and duration of the spontaneous uterine concentrations were irregular in all strips recorded independent of reproductive stage. The spontaneous activity was most pronounced during the follicular phase. The variation between animals was greatest for cystic cows. PGF2 alpha always increased the activity of the uterus but the response was not dose related above a certain level (50 ng per ml bath fluid). Oxytocin on the other hand had a linear stimulatory effect for increasing doses (0.25, 2.5 and 25 mIU per ml bath fluid).

Progesterone production by dispersed cells from human corpus luteum: stimulation by gonadotrophins and prostaglandin F 2 alpha; lack of response to adrenaline and isoprenaline

Progesterone production was assessed following short-term incubations of luteal cell suspensions prepared from tissue samples of human corpora lutea obtained at specific times throughout the luteal phase of the menstrual cycle. Luteal cells responded rapidly and sensitively to human chorionic gonadotrophin (HCG: concentration required for 50% maximum response, 0.1--1.0 i.u./ml) with a maximum level of response (five- to tenfold higher than basal production) similar to that elicited by human LH or N6,O2'-dibutyryl cyclic AMP. In the absence of gonadotrophin or in the presence of sub-maximal (but not maximal) concentrations of HCG, progesterone production by mid-luteal phase cells was stimulated by prostaglandin F 2 alpha (1 mumol/l, an effect not observed during the late-luteal phase. L-Adrenaline and L-isoprenaline failed to elicit significant increases in the level of progesterone production.

Regulation of adipocyte insulin receptor number and metabolism during late-pregnancy

The regulation of the rate of fatty acid synthesis of rat adipose tissue during late-pregnancy has been investigated. Rats at day 18 of pregnancy were injected over a 2-day period with either prostaglandin F2 alpha (PGF2 alpha), PGF2 alpha plus progesterone, PGF2 alpha plus bromocriptine or carrier solutions, and were then killed on day 20 of pregnancy. Injections of PGF2 alpha resulted in a decreased rate of fatty acid synthesis, a lower serum-insulin concentration, and a reduced number of insulin receptors of adipocytes. Concurrent injections of progesterone, but not of bromocriptine, along with the PGF2 alpha prevented these effects of the latter. The results are consistent with our previous suggestion that the fall in serum progesterone concentration prior to parturition results in a reduction in the number of insulin receptors of adipocytes, which, along with a fall in the serum-insulin concentration, leads to a decrease in the anabolic activity of the tissue.

Potent bronchoconstrictor effects of aerosolized prostaglandin D2 in dogs

Previously, we demonstrated that prostaglandin D2 (PGD2), a natural product of the endoperoxide PGH2, evoked bronchoconstriction when given I.V. to dogs (PROSTAGLANDINS 13:255-269, 1977). The present investigation in anesthetized dogs demonstrated that aerosols of PGD2 (0.001-0.1%) produced concentration-dependent increases in pulmonary resistance (RL) and decreases in dynamic lung compliance(CDYN) which were short-lived and equipotent to PGF2 alpha. These alterations in pulmonary mechanics were partially, yet significantly, inhibited by atropine, thereby suggesting that at least a portion of the bronchoconstriction may be cholinergically mediated. Concomitant cardiovascular depressant effects of both PGD2 and PFG2 alpha aerosols were much less and more variable than their bronchopulmonary effects. These results demonstrate a potent bronchoconstrictor effect of aerosolized PGD2 in dogs. PGD2 warrants further attention as a possible mediator of the bronchospasm seen in acute, reversible airways obstruction.

An invitro study on the effect of prostaglandin E2 and F2 alpha on E-rosette forming activity of normal lymphocytes

The effects of PGE2 and F2 alpha have been studied on E-rosette forming activity of normal human peripheral blood lymphocytes. Addition of both PGs into the incubation medium caused a significant and concentration - dependent inhibition of E-rosette formation. The minimum effective concentration of both PGs was found to be 10(-9) M and complete inhibition was obtained when the concentration was increased to 10(-7) M. Possible mechanisms of the action of PGs on E-rosette formation are discussed.

Modulation of cyclic AMP content of the rat myometrium: desensitization to isoproterenol, PGE2 and prostacyclin

Exposure of the oestrogen-dominated rat myometrium to either isoproterenol or PGE2 resulted in a rapid but transient accumulation of cyclic AMP, with a progressive loss of responsiveness to the corresponding agonist. Induction of refractoriness was a time- and dose-related phenomenon. In the earliest time, desensitization was agonist-specific but was followed, with continued exposure, by a cross desensitization between isoproterenol and PGE2 and vice versa. Differential time courses for development and reversal of specific and heterologous refractoriness indicate at least 2 different processes for the 2 phenomena, the non-specific type being possibly mediated by cyclic AMP. Exposure to isoproterenol or PGE2 also caused an attenuated cyclic AMP response to prostacyclin (PGI2). Kinetics for PGE2-induced desensitization to PGI2 were comparable to that of an agonist-specific refractoriness, indicating that PGE2 and PGI2 may share common receptor sites. PGF2 alpha, PGD2 and 6-keto PGF1 alpha, which contract the myometrium but are ineffective on adenylate-cyclase activity, did not promote cyclic AMP refractoriness to PGE2, PGI2 or isoproterenol. Isoproterenol also caused refractoriness to its own relaxing activity, whereas PGE2 did not affect isoproterenol-induced relaxation despite a marked attenuation of the beta-adrenergic response to cyclic AMP. These results provide further evidence for the non-exclusive role of cyclic AMP in mediating uterine relaxation.

A luteolytic effect of a prostaglandin F2 alpha analogue in non-pregnant women?

Four healthy non-pregnant volunteers with regular cycles were exposed to vaginal suppositories containing a PGF2 alpha analogue (ICI 81.008, 500-600 microgram) twice at 24-hour intervals in the early or mid-luteal phase. In comparison to serum progesterone levels of ovulatory control cycles, this treatment caused a significant decrease of serum progesterone combined with a shortening of the length of the luteal phase by 1.4 days. No gastrointestinal or other adverse effects were noticed during this treatment. Administration of ICI 81.008 in the follicular phase interfered neither with ovulation nor with the length or shape of the following luteal phase. Although limited, these data suggest a luteolytic effect of ICI 81.008 in women.

Spontaneous contractility of human placental vessels in vitro axipetal and isometric recording

In vitro contractility of isolated cylindrical segments of chorial arteries and veins from 40 human term placentas was studied. Contractility was recorded by an isometrical and axipetal method. Spontaneous contractility was observed in 75% of the arteries and in 45% of veins. In both types of vessels, contractility was similar and characterized by development of tonic circumferential tension, between 100 and 200 mg/mm. Clonic activity consisting of rhythmic contractions with an average frequency between 0.7 and 0.9/min and an average intensity of 5--40 mg/min was superimposed. Vasoconstrictor drugs (PGF2 alpha, histamine and adrenaline) increase tonic tension without modifying the frequency of clonic activity. It is suggested that spontaneous contractility may be the expression of myogenic excitability related to the regulation of fetal placental blood flow.

The effects of prostacyclin (PGI2) and 6-keto-PGF1 alpha on bovine plasma progesterone and LH concentrations

Injections of 1 mg PGI2 directly into the bovine corpus luteum significantly increased peripheral plasma progesterone concentrations within 5 min. Concentrations were higher in the PGI2-treated heifers than in saline-injected controls between 5 and 150 min and at 3.5, 4, 5, and 7 h post-treatment. Levels tended to remain elevated through 14 h. Saline and 6-keto-PGF1 alpha were without effect on plasma progesterone levels. The luteotrophic effect of PGI2 was not due to alterations in circulating LH concentrations. An in vitro experiment assessed the effects of either PGI2 alone or in combination with LH on progesterone production by dispersed luteal cells. Progesterone accumulation over 2 h for control, 5 ng LH, 1 microgram PGI2, 10 micrograms PGI2, and 10 micrograms PGI2 plus 5 ng LH averaged 99 +/- 42, 353 +/- 70, 152 +/- 35, 252 +/- 45, and 287 +/- 66 ng/ml (n = 4), respectively. Thus PGI2 has luteotrophic effects on the bovine CL both in vivo and in vitro.

Prostacyclin and thromboxane A2 synthesis by rabbit pulmonary artery

Superfused spiral strips of rabbit intrapulmonary artery (i.p.a.) were contracted by arachidonic acid (AA) and by the following substances in order of potency: prostaglandin (PG) endoperoxide analog (U46619) > PGH2 > PGF2 alpha. Intrapulmonary artery strips were consistently relaxed by PGE2 and by the enzyme inhibitors, indomethacin, aspirin, meclofenamic acid and 1-pentylimidazole. These latter inhibitors of cyclooxygenase and thromboxane (TX) synthetase also blocked the AA-induced contraction of rabbit i.p.a. Prostacyclin had no effect on the i.p.a. or produced either a small contraction or relaxation. TXA2, formed by incubating horse platelet microsomes with PHG2, always contracted the tissue and was more potent than the parent endoperoxide. Incubations of [14C]AA with i.p.a. produced mainly [14C]-6-keto-PGF1 alpha (he breakdonw product of prostacyclin ) and [14C]TXB2 (the breakdown product of TXA2); the identities of these products were confirmed by radioimmunoassay and by gas chromatography-mass spectrometry. The synthesis of TXB2 by i.p.a. cannot be attributed to adhering lung tissue or platelets and appears to be produced by the vascular tissue itself. It is concluded that, although both prostacyclin and thromboxane may contribute to the resting tone of the rabbit i.p.a., the response to AA is mainly due to production of TXA2.

Intravesical prostaglandin: release and effect of bladder instillation on some micturition parameters

Bladder washout effluent fluid was examined for prostaglandin-like activity following acidic lipid extraction and bioassay using the rat-stomach strips technique. A low basal level of prostaglandin-like material was detected in washouts collected when the bladder was empty in 4 out of 7 dogs. Increased levels were detected following micturition in 5 of these 7 dogs. A significantly high level of prostaglandin-like material was recovered after pelvic nerve stimulation. The prostaglandin-like material was tentatively identified as PGE based on the bioassay with the addition of specific antibody. Intravesically administered PGE2 or PFG2 alpha significantly reduced, in a dose-dependent response, the threshold micturition volume. All of these findings suggested that prostaglandins may play a role in the micturition process.

[Effect of prostaglandin F2 on the bladder muscles in women]

The effect of intravenous Pg F2 alpha on the detrusor muscle in young healthy females during filling cystometry and during a long period of pressure normalization was studied. It was possible to induce uninhibited detrusor contractions in two thirds of the cases, very much resembling those of patients with motor-urge-incontinence. The sensitivity of the uterus was found to be higher than that of the bladder. Both organs responded with a gradual tone increase followed by regular contractions of the uterus and more erratic contractions of the detrusor. Therapeutic studies with a Pg-synthesis inhibitor (Indometacin) were undertaken with moderate success.

The degenerative effect on rabbit implantation sites by indomethacin. I. Timing of indomethacin action, possible effect on uterine proteins and the effect of replacement doses of PGF2 alpha

To determine the effective time of indomethacin (Id) action in disrupting early pregnancy, groups of rabbits were treated at various stages after mating with Id and/or replacement doses of PGF2 alpha. Effect of Id on the secretion of uterine proteins was also investigated. The highest rate of embryonic death occurred when Id was injected twice daily during days 5-7 of pregnancy, and days 5-6 appear to be the most critical. Persisting levels of Id during this critical stage is required to induce the antifertility effect. The results also indicate that the adverse effect of Id is not mediated through an effect on uterine proteins, and is mainly due to the inhibition of PG's synthesis. PG's are apparently required for normal implantation and early development.

Pharmacoangiography of gynecologic tumors

Angiography was performed before and after intraarterial administration of prostaglandin F2 alpha, 8-lysine vasopressin, oxytocin, methylergometrine, noradrenalin, and bradykinin in 62 women with various pelvic tumors. It is concluded that the use of the vasoactive drugs in the doses tested did not improve the angiographic diagnosis in unselected cases of female pelvic tumors.

Effect of prostaglandins on ornithine decarboxylase activity in the testis of immature rat

Intratesticular injection of prostaglandin E2 (PGE2) and F2 alpha (PGF2 alpha) caused stimulation of ornithine decarboxylase (ODC) activity in the testis of immature rats. PGE2 at a dose of 10 microgram per testis was maximally effective 2 hours after the injection. Dibutyryl cyclic AMP (cAMP) and 1 methyl, 3-isobutyl xanthine (MIX), a phosphodiesterase inhibitor, also stimulated ODC activity. Simultaneous injection of PGE2 and FSH or LH caused additional stimulation of ODC activity. Similarly injection of PGE2 in addition to cAMP or MIX also caused increased stimulation of ODC. Indomethacin (IM, 60 microgram/testis) inhibited LH, FSH or cAMP induced ODC activity. However, IM at the same dose inhibited the synthesis of total proteins. These results suggest that PGE2 and PGF2 alpha stimulate the activity of ODC. The action of prostaglandins may be independent of the action of gonadotropic hormones. cAMP appears to mediate the action of prostaglandins in the testis of rat.

Influences of prostaglandins on electrophoretic mobility and aggregation of rabbit platelets

Influences of prostaglandin (PG)s on electrophoretic mobilities and aggregation of rabbit platelets were studied. The PGs studied (PGI2, PGE1, PGD2, PGF2 alpha, PGA2 and PGA1) had no effect on platelet electrophoretic mobility. However, both PGE1 and PGI2 in 0.3 and 3.0 muM inhibited ADP-induced aggregation and ADP-induced decrease in the mobility. PGD2 in 0.3 and 3.0, and PGE2 in 30 microM inhibited the aggregation but did not depress the ADP-induced decrease in the mobility. PGF2 alpha, PGA2 and PGA1 had no effect on the decrease in electrophoretic mobility and on the aggregation caused by ADP.