response of relaxin-treated rat uterus to prostaglandins and oxytocin

Paired segments of rat uterus were treated with relaxin (W1164-3, 150 GPU/mg) until the amplitude of contraction was reduced to at least 50% of the pre-treatment amplitude. Test segments then received 100 ng of either PGE₁, PGE₂, PGF_2α or 250 uU of oxytocin. Control segments remained untreated. There was a significant increase in contraction amplitude in response to the spasmogens (P < 0.05) but no increase was seen in controls.     

Prostaglandin-induced enhancement of the in vitro anamnestic response

The ability of various prostaglandins (PGs) to affect the $\text{in vitro}$ anamnestic immune response of keyhole limpet hemocyanin (KLH)-primed rabbit popliteal lymph node cells was investigated. Of the four PGs studied (PGA₁, PGE₂ and PGF_2α), PGE₁ was found to have a stimulatory effect, whereas PGA₁, PGE₂ and PGF_2α were ineffective in stimulating or inhibiting the $\text{in vitro}$ anamnestic response. Under the conditions studied, a 3.5-fold increase in antibody production was obtained in PGE₁-treated, KLH-stimulated cultures. Maximum enhancement was obtained when 0.2 μg of PGE₁ were added at the time of culture initiation and were allowed to remain in contact with the lymph node cells for 24 hours.     

Potentiation of bradykinin-induced vascular permeability increase by prostaglandin E2 and arachidonic acid in rabbit skin

The activity of prostaglandins (PG) in producing vascular permeability was quantitated by dye extraction method in skin of anaesthetized rabbits. PGE₁ and PGE₂ (0.01–10 μg) produced increase in vascular permeability. Activity was approximately equal to that of histamine (Hist) and $\text{1}\text{20}$ of that of bradykinin (BK) on a weight basis. The activity of PGF_1α and PGF_2α was only $\text{1}\text{20}$ of that of PGE₁ or PGE₂.In spite of the relatively low potency of PGE₁ and PGE₂ in the rabbit, near threshold doses (0.1 or 1 μg) of PGE₂ could potentiate permeability responses to bradykinin (0.1 μg) by 10 or 100-fold, respectively. Equivalent doses (0.1 or 1 μg) of histamine could not potentiate the bradykinin responses. Arachidonic acid (AA) at 1 μg, produced a 10-fold potentiation in the permeability response to bradykinin (0.1 μg). Pretreatment of the rabbits with indomethacin (20 mg/kg, i.p.) reduced the responses of BK (0.1 μg) + AA (1 μg) down to a similar magnitude of those seen with bradykinin alone. However, indomethacin did not block responses to either, BK alone, BK + PGE₂, or BK + Hist. Various doses (1, 10, 100 and 300 μg) of arachidonic acid alone also produced increase in cutaneous vascular permeability, although its potency was only $\text{1}\text{3}$–$\text{1}\text{8}$ of that of PGE₂. This activity of arachidonic acid was attributed in part to its bioconversion to PGE₂, since its activity was significantly reduced by the prostaglandin antagonist, diphloretin phosphate (DPP) (60 mg/kg, i.v.) and by indomethacin (20 mg/kg, i.p.), which blocks conversion of arachidonic acid to prostaglandins. Arachidonic acid may owe some of its permeability increaseing effects to histamine release, since its effects were also reduced by the antihistamine, pyrilamine (2.5 mg/kg, i.v.).     

Role of endogenous and exogenous prostaglandins on the contractile functioning of isolated sow (Sus scrofa) oviducts

The output prostaglandins (PHs) E₁, E₂ and F₂ α, from ampullary and isthmic portions of sow oviducts isolated during proestrus, estrus and metestrus, was explored. Moreover, $\text{in vitro}$ cumulative dose-response curves for the contractile effect of these three PGs, on identical oviductal segments, were constructed. Isthmic preparations form proestrous and metestrous animals released more PGE₁ and PGF₂ α than PGE₂ “like material”. During estrus, the outputs of PGE₁, PGE₂ and PGF₂ α were similar, whereas, oviducts from proestrous and metestrous sows released less PGE₁ and PGF₂ α than during estrus. Although the output of PGE₂ “like material” from isthmic and ampullary segments did not differ significantly during the three stages of the sex cycle, ampullary metestrous preparations released more PGE₁ and PGF₂ α, than estrous or proestrous ones. The addition of PGE₁, PGE₂ α, consistently stimulatedthe amplitude of contractions of isthmic oviductal segments isolated from proestrous and metestrous sows. Within the concentration-range explored, dose-response curves for PGE₂ and PGE₁ were to the left of those for PGF₂ α in the isthmus obtained before ovulation (proestrus) but not in segments isolated at later times (2–3 days) of the cycle (metestrus). The stimulatory dose-response curves for PGE₁, or PGE₂, in isthmic segments of metestrous preparations incubated with phentolamine (10^?6M) were shifted to the right of controls not exposed to the adrenoreceptor blocker, whereas, the curve for PGF₂ α without phentolamine, was identical to that obtained in its presence. PGE₁ and PGE₂ did not evoke significant contractile effects on oviductal ampullary protions from proestrous sows, wherea, PGF₂ α was clearly stimulatory at concentrations of 10^?9M and higher. In ampullary segments isolated after ovulation (metestrus) the threshold for contractile enhancement following PGF₂ α was greater than during proestrus, whereas, PGE₁ elicited a significant inhibition of contractions. The spontaneous contractile pattern exhibited by isthmic and ampullary oviductal regions, prior to and after ovulation, is discussed in terms of tissue PG generation and output and is compared with results regarding tubal motility following the exposure to exogenous PGs.     

Effects of 19-hydroxy-prostaglandins on oviductal and uterine motility

The effects of 19-hydroxy-prostaglandins (19-OH-PGs) were tested $\text{in}$$\text{vivo}$ on the rabbit oviduct and uterus and on the rhesus monkey ($\text{Macaca}$$\text{mulatta}$) uterus. The 19-OH-PGEs suppressed spontaneous oviductal and uterine activity in the rabbit. The qualitative effect on the rabbit oviduct of 19-OH-PGEs was similar to that of PGE₂. However, the typical response of the rabbit uterus to PGE₂ was an increase in muscle activity. With regard to the rabbit oviduct, 19(R)-OH-PGE₂ was as potent as PGE₂, but 19(S)-OH-PGE₂ was approximately $\text{1}\text{2}$ as potent as PGE₂. Based on the dose of 19-OH-PGEs usually required to cause a minimal suppression and the dose of PGE₂ required to cause a minimal stimulation of rabbit uterine activity, 19(R)-OH-PGE₂ was twice as potent as PGE₂ while 19(S)-OH-PGE₂ was $\text{1}\text{2}$ as potent as PGE₂. Stimulatory effects on the rabbit oviduct and uterus were observed following administration of 19-OH-PGEs and PGF_2α. The potency on the rabbit oviduct of 19(S)-OH-PGF_2α was about $\text{1}\text{5}$ to $\text{1}\text{10}$ that of PGF_2α; the potency of 19(R)-OH-PGF_2α was about $\text{1}\text{10}$ to $\text{1}\text{20}$ that of PGF_2α. Both 19-OH-PGFs were approximately $\text{1}\text{5}$ to $\text{1}\text{10}$ as potent as PGF_2α on the rabbit uterus. At the doses tested 19-OH-PGFs were inactive on the monkey uterus. Thus, these compounds are at least $\text{1}\text{5}$ as active as PGF_2α. In contrast, 19(R)-OH-PGE₂ had approximately the same potency as PGE₂ in stimulating monkey uterine activity; but 19(S)-OH-PGE₂ was approximately $\text{1}\text{3}$ as potent as PGE₂.     

Bronchodilator activity of a PGE2 analog in animals and in man

A C-11 substituted PGE₂ analog, DHET-PGE₂ [$\text{?}$-11-deoxy-11α-(2-hydroxyethylthio)-PGE₂ methyl ester], was demonstrated to exert potent bronchodilator activity in three $\text{in vivo}$ models of augmented airway resistance: (1) acute bronchospasms, induced by 5-hydroxytryptamine, histamine and acetylcholine in the anesthetized guinea pig, (2) acute bronchospasm, induced by pilocarpine, in the anesthetized dog, and (3) chronic bronchospasm, induced by SO₂ exposure, in the unanesthetized dog. In acute and 30-day toxicological studies in the dog, no cardiovascular, respiratory or gastrointestinal side effects were observed at aerosol doses at least 1,000 times those required for efficacy. $\text{In vitro}$, DHET-PGE₂ effectively relaxed isolated preparations of dog bronchus that had been contracted with carbachol. In clinical studies, human asthmatics and bronchitics responded consistently to β-agonist bronchodilators but variably to DHET-PGE₂. Overall, increases in pulmonary resistance or decreases in FEV₁ were observed with DHET-PGE₂. Subsequent evaluation in isolated carbachol-contracted human bronchus revealed that, in contrast to the bronchodilator activity of PGE₁ and β-agonists, DHET-PGE₂ and PGE₂ induced contraction. Considered along with results from previous clinical studies on other PGs, these data underscore the difficulties in making extrapolations on this class of compounds from animal models to humans and suggest that human bronchial tissue may provide the only appropriate preclinical test system for predicting the clinical efficacy of PG bronchodilators.     

Prostaglandin synthesis in rabbit renal medulla.

Prostaglandin (PG) synthesis in rabbit renal medullary homogenates was investigated by gas chromatography-mass spectrometry utilizing two internal standards. The internal standards were added immediately after homogenization to an aliquot of the fresh homogenate. Another aliquot of the homogenate was incubated and subsequently the internal standards were added. The internal standards were 3,3,4,4 tetradeutero PGE₂(d₄-PGE₂) for quantification of PGE₂, the PGA₁ for quantification of PGA₂ and 3,3,4,4 tetradeutero PGA₂, the latter representing an $\text{in}$$\text{vitro}$ dehydration product of d₄-PGE₂ generated during work up of the samples. In 6 experiments on 6 rabbits levels of PGE₂ were 4.4 ± 1.6 μg/g (mean ± SD) renal medulla increasing during incubation to 14.95 ± 6.5 μg/g (p < 0.01) PGA₂ levels were 0.03 ± 0.02 μg/g in the non-incubated samples and did not increase during incubation. When PGA₂ levels were corrected for the amount of PGA₂ formed by $\text{in virto}$ dehydration from PGE₂ as measured by the amount of d₄-PGE₂ dehydrated to d₄-PGA₂ during workup, PGA₂ levels were indistinguishable from zero.     

Developmental response to indomethacin: A comparison of isometric tension with PGE2 formation in the lamb ductus arteriosus

We studied the effects of oxygen and indomethacin on the isometric contractile response and the production of PGE₂ in isolated rings of lamb ductus arteriosus from animals of different gestational ages (100 to 144 days; term is 150 days). Rings of ductus arteriosus from animals less than 110 days released significantly less PGE₂ than did rings from animals greater than 120 days. The indomethacin-induced increase in muscle tension in relation to the decrease in endogenous PGE₂ production in preparations from animals less than 110 days gestation was greater than in animals older than 120 days. These findings do $\text{not}$ support the hypothesis that immature animals have a larger indomethacin-induced contraction due to an increased production of PGE₂ earlier in gestation. They are, however, consistent with a decreased sensitivity to PGE₂ in the more mature animals; they also support the hypothesis that the decreased effectiveness of indomethacin on the ductus arteriosus from later gestation animals reflects primarily a decrease in the sensitivity of the vessel to PGE₂ during development.     

Prostaglandin endoperoxides IV. Effects on smooth muscle

The effect on smooth muscle of the endoperoxides PGG₂ and PGH₂, which are intermediates in prostaglandin biosynthesis, was studied in different systems $\text{in vitro}$ and $\text{in vivo}$. On gastrointestinal smooth muscle (gerbil colon, rat stomach) PGG₂ and PGH₂ produced contractions comparable to those of PGE₂ and PGF_2a whereas contractions elicited on vascular (rabbit aorta) and airway (guinea-pig trachea) smooth muscle were considerably greater than those of PGE₂ and PGF_2a respectively. On intravenous injection into guinea-pigs PGG₂ and PGH₂ caused a triphasic change in blood pressure and were 8–10 times more effective than PGF_2a in producing an increase in tracheal insufflation pressure. When given as aerosols the unstable endoperoxides were less effective than PGF_2a. It is concluded that the endoperoxides are potent smooth muscle stimulants and that they are more effective than their degradation products (PGD₂, PGE₂, PGF_2a) in some systems.     

Effects of prostaglandin PGE2 on the synthesis of placental proteins and human placental lactogen (HPL)

The biosynthesis of placental proteins and placental lactogen (HPL) was studied $\text{in vitro}$ in 10–12 week, 16–18 week and term human placenta in the presence and absence of PGE_2α. The highest ¹⁴C-leucine incorporation was detected in 10 to 12 weeks old placentas. Addition of PGE_2α to the induction medium depressed the rate of incorporation of ¹⁴C-leucine into placental proteins on a dose dependent manner. Placentas most sensitive to this action of PGE_2α were those obtained at 18 weeks gestation followed by placentas at term. $\text{In vivo}$ application of PGE_2α for tharapeutic induction of abortions resulted in the marked inhibition of placental protein synthesis $\text{in vitro}$.     

Nasal vasoconstrictor activity of a novel PGE2 analog

A novel PGE₂ analog (CL 116,069) was shown to be effective in dogs as a nasal decongestant. Threshold doses were approximately 0.1 μg/kg with intravenous administration and between 0.08 and 4 μg with topical administration. CL 116,069 was compared to 17-phenyl-trinor PGE₂ (CL 116,147), a compound recently studied in humans, and xylometazoline, a well-known nasal decongestant. When given i.v., efficacious doses of xylometazoline tended to raise blood pressure and be shorter acting than the PGs, which did not affect blood pressure. When given topically, all three were long-acting. CL 116,069 usually had the lowest threshold and CL 116,147 usually induced the smallest response. All three agents were more effective than PGE₁ or PGE₂. A 30-day (b.i.d., topical) toxicity test with CL 116,069 produced no inflammation or nasal pathology and no loss in tissue sensitivity. $\text{In}$$\text{vitro}$ examination of xylometazoline and CL 116,069 for vascoconstrictor activity on dog isolated mucosa revealed a response profile similar to that observed with these agents $\text{in}$$\text{vivo}$; i.e., the magnitude of response was comparable for both agents but the t $\text{1}\text{2}$ was only 74 minutes for xylometazoline and greater that 6.5 hours for CL 116,069. The data suggest that CL 116,069 may provide a therapeutic alternative in which constriction of the nasal blood vessels need not be associated with a generalized vasoconstrictor liability.     

Relative contracting adn relaxing potencies of a series of prostaglandins on isolated canine mesenteric artery strips

The contracting and relaxing potencies of anf interactions between a number of prostaglandins (PGs) were studied $\text{in vitro}$ on spiral strips of small canine mesenteric arteries (outside diameter < mm). PGF₂α and PGE₂, the most potent contracting PGs, were nearly equal in potency (EC₅₀ 4 × 10^?7M) and did not cause relaxation under our experimental conditions. PGI₂ and PGE₁ were equal and the most potent relaxing PGs (EC₅₀ 3 × 10^?9M). PGE₁ also caused contraction, but this effect was not consistent. PGI₂ did not cause contraction in concentrations up to 3 × 10^?6M. In higher concentrations, however, it caused abrupt and near maximal contraction. PGD₂ was weak in both respect, causing incomplete relaxation and contraction or biphasic effects. Interaction studies showed that PGE₁ and PGI₂ mutually excluded the relaxing effects of each other. PGE₁ also reversed the relaxing effect of isoproterenol. However, pre-exposure to PGD₂ did not attenuate the relaxing effect of PGE₁ or PGI₂ nor was the relaxing effect of PGD₂ changed by pre-exposure to PGE₁. Two different orders of potency of PGs suggest two PG receptors subserving contraction and relaxation, respectively. Further, it appears that several PGs can act upon both receptors which may explain unusual interactions between the PGs and some of their atypical effects. Finally, the data also suggest that there may be subtypes of the PG receptors subserving contraction and relaxation.     

Effects of hydrocortisone on the hypercalcemia and plasma levels of 13,14-dihydro-15-keto-prostaglandin E2 in mice bearing the HSDM1 fibrosarcoma

In mice bearing the prostaglandin-producing HSDM₁ fibrosarcoma, the plasma concentration of 13,14-dihydro-15-keto-PGE₂ was elevated before the development of hypercalcemia, and the magnitude of the rise was greater than that of PGE₂. When hydrocortisone, which inhibits synthesis of PGE₂ by HSDM₁ cells in culture, was administered to tumor-bearing mice, the steroid hormone prevented the rises in plasma PGE₂ metabolite and calcium concentrations. At the dose levels used, hydrocortisone did not inhibit the calcium-mobilizing action of parathyroid hormone $\text{in vivo}$ or the bone resorption-stimulating activity of $\text{PGE}{}_2\text{in vitro}$. These findings are consistent with our hypothesis that the hypercalcemic syndrome in HSDM₁ tumor-bearing mice is due to the secretion of PGE₂ by the tumor.     

Effects of arachidonic acid and its cyclo-oxygenase and lipoxygenase products on lymphatic vessel contracility in vitro

Lymphatic vessels exhibit rhythmical contractility $\text{in vivo}$ and $\text{in vitro}$ and this activity appears ti regulate lymph flow. A technique for measuring the cicurlar muscle contractions of isolated bovine mesenteric lymphatic vessel segments has been devised and utilized to study the pharmacological properties of these vessels. Non-contracting lympahtic vessels can be induced to contract rhythmically with a variety of mediators, the most potent being a stable PGH₂ analogue (compound U46619), and the leukotrienes B₄, C₄ and D₄ (threshold concentrations in the nanomolar range). Prostagladin F_2α, noradrenaline, serotonin and histamine also elicited rhythmical activity but much higher concentrations were required. PGE₂ and PGE₁ were potent inhibitors of spontaneous contractions or those induced with U46619. In keeping with the diverse pharmacological effects of the metabolites of arachidonic acid, the addition of arachidonate to an isolated lymphatic vessel generated both stimulatory and inhibitory activities.It is concluded that arachidonic acid products (produced in the lymphatic vessel or entering the vessel in lymph draining the tissues) regulate lymph flow through their effects on lymphatic smooth muscle.     

Intraperitoneal injection of zymosan in mice induces pain,inflammation and the synthesis of peptidoleukotrienes and prostaglandin E2

Intraperitoneal injection of zymosan in mice induced rapid extravasation and accumulation of plasma proteins in the peritoneal cavity. Neutrophils began to appear in the peritoneal cavity after a lag period of approximately 3 hours. The injected mice exhibited a pain response (writhing) during the first 30 minutes after injection, but writhing ceased before protein or cell accumulation had reached maximum levels. The injection of zymosan induced synthesis of PGE₂ (measured by RIA) which reached maximum levels of 30 minutes, then declined slowly. Peptido-leukotriene levels (detected by bioassay, RIA and HPLC) increased rapidly after injection, reached a peak within an hour of injection and declined to undetectable levels within 4 hours. The early peptido-LT was predominantly LTC₄, while later, LTE₄ was the major component. LTD₄ levels remained low throughout and no LTB₄ was detected at any time. Indomethacin treatment elevated levels of peptido-LTs, recued PGE₂ levels and inhibited writhing. Phenidone reduced peptido-LT levels. $\text{In}$$\text{vitro}$ studies demonstrated that zymosan stimulates LTC4 synthesis by peritoneal cells whereas LTE₄, LTD₄, LTB₄ or monoHETES were not detectable (using HPLC methods). The source of enzymes responsible for the $\text{in}$$\text{vivo}$ metabolism of LTC₄ to LTD₄ and LTE₄ could not be identified.     

Interactions of prostaglandins with subpopulations of ovine luteal cells. I. Stimulatory effects of prostaglandins E1, E2 and I21

Preparations of small and large steroidogenic cells from enzymatically dispersed ovine corpora lutea were utilized to study the $\text{in}$$\text{vitro}$ effects of luteinizing hormone (LH) and prostaglandins (PG) E₁, E₂ and I₂. Cells were allowed to attach to culture dishes overnight and were incubated with either LH (100 ng/ml), PGE₂, PGE₂, or PGI₂ (250 ng/ml each). The secretion of progesterone by large cells was stimulated by all prostaglandins tested (P < 0.05) while the moderate stimulation observed after LH treatment was attributable to contamination of the large cell population with small cells. Prostaglandins E₁ and E₂ had no effect on progesterone secretion by small cells, while LH was stimulatory at all times (0.5 to 4 hr) and PGI₂ was stimulatory by 4 hr. Additional studies were conducted to determine if the effects of PGE₂ upon steroidogenesis in large cells were correlated with stimulated activity of adenylate cyclase. In both plated and suspended cells PGE₂ caused an increase (P < 0.05) in the rate of progesterone secretion but had no effect upon the activity of adenylate cyclase or cAMP concentrations within cells or in the incubation media. Exposure of luteal cells to forskolin, a nonhormonal stimulator of adenylate cyclase, resulted in marked increases in all parameters of cyclase activity but had no effect on progesterone secretion. These data suggest that the actions of prostaglandins E₁, E₂ and I₂ are directed primarily toward the large cells of the ovine corpus luteum and cast doubt upon the role of adenylate cyclase as the sole intermediary in regulation of progesterone secretion in this cell type.     

Prostaglandin E2 rather than lymphocyte-activating factor produced by activated human mononuclear cells stimulates increases in murine thymocyte cAMP

Culture supernatants (SUPS) of endotoxin (LPS)-activated human mononuclear cells (MNL) stimulated greater production of cAMP by thymocytes than by spleen cells of C3H/HeJ or nude ($\text{nu}\text{nu}$) mice. Similarly, the addition of prostaglandin E₂ (PGE₂) stimulated higher levels of cAMP in thymocytes and progressively lower levels in spleen cells from C3H/HeJ mice and $\text{nu}\text{nu}$ spleen cells, respectively. Partial purification on Bio-Gel P100 of the LPS-induced MNL SUPS yielded peaks of thymocyte proliferative activity characteristic of lymphocyte activation factor (LAF) but these fractions failed to stimulate cAMP levels in thymocytes. Moreover, MNL SUPS induced with LPS in the presence of indomethacin retained their LAF activity but no longer increased thymocyte cAMP levels. Radioimmunoassay of the SUPS for PGE₂ revealed significantly higher levels of PGE₂ in the media of those MNL cultures stimulated by LPS than when stimulated by phorbol myristic acetate, phytohemagglutin, or extracted cell wall fraction of Actinomyces viscosus. Thus, PGE₂ is produced by human MNL and may exert considerable immunoregulatory effects mediated by elevation of lymphocyte cAMP levels.     

Decreased smooth muscle side effects with 16, 16-dimethyl-trans-Δ2-PGE1 methyl ester in Japanese monkey (Macaca fuscata fuscata)

The smooth muscle stimulating activity of a new PGE₁ analog, 16, 16-dimethyl-trans-Δ²-PGE₁ methyl ester (ONO-802) was evaluated by simulataneous;y recording the EMG of the uterus and intestines, along with urinary bladder pressure, and blood pressure in pregnant and non-pregnant Japanese monkeys ($\text{Macaca fuscata fuscata}$). Single intravenous injections of ONO-802 in increasing dosages (0.2–5 μg/kg) were found to be 50–100 times or more effective in inducing uterine contraction than PGF₂α and PGE₁. A mild, transient gastrointestinal muscle stimulating activity was observed, but change in urinary bladder pressure and blood pressure was not evident. ONO-802 induced uterine contractions in the pregnant animals were 10 times greater than in the non-pregnant animals. These results suggest that ONO-802 may be a suitable clinical prostaglandin for use in therapeutic abortion.     

Stimulatory effect of prostaglandin E1 on thyroliberin-induced α-melanotropin release from perifused neuro-intermediate lobes of frog pituitary gland

A possible direct effect of prostaglandins on α-melanotropin (α-MSH) release at the level of the intermediate lobe of the frog pituitary was investigated $\text{in vitro}$ using a perifusion system technique. The effect of prostaglandins was studied on both spontaneous and TRH-stimulated α-MSH secretion. No significant effect of PGE₁, PGE₂, PGF_1α or PGF_2α on basal release of α-MSH could be detected. Indomethacin did not alter the α-MSH release induced by TRH. Conversely a significant increase in TRH-induced α-MSH secretion was observed in the presence of 1 x 10^?6M PGE₁. This magnifying effect was directly related to the concentration of TRH for doses ranging from 1 x 10^?8M to 1 x 10^?6M.     

The measurement of human endometrial prostaglandin production a comparison of two in vitro methods

Two $\text{in vitro}$ methods for measuring human endometrial prostaglandin production were compared. Endometrial samples from eight patients were incubated over eight hours by a perifusion and a superfusion technique. The collected fractions were assayed by radioimmunoassay for PGE₂ and PGF_2α.There was no significant difference between the perifusion and superfusion methods for the pattern and amount of PGE₂ and PGF₂ production with time. Significantly higher production levels of PGE₂ and PGF_2α were found in secretory phase endometria than in proliferative phase endometria. Histological examination of the tissue specimens by light and electron microscopy showed that both methods caused gross tissue damage after eight hours experimentation. The superfusion method produced more morphological damage than the perifusion method. However, no tissue damage could be detected after one hour of incubation with either method.Over an eight hour period neither the perifusion nor the superfusion technique appears to be a good indicator of $\text{in vivo}$ endometrial prostaglandin production. Either reflect the $\text{in vitro}$ situation.