A dose-response comparison of PGA2, PGE1 and PGE2 using the phenylephrine-stimulated perfused oviduct of the rabbit

The phenylephrine-stimulated perfused oviduct of the rabbit was evaluated as a model for studying the activity of prostaglandins that produce inhibition of the oviducal smooth muscle. Elevation of the normal “tone” of the oviduct by perfusing phenylephrine through the lumen permitted quantitation of the responses to PGA₂, PGE₁ and PGE₂ by measuring the magnitude of the inhibitory response produced by the agents. PGE₂ was relatively more potent, efficacious and specific for the oviduct than PGA₂ or PGE₁. It was concluded that the model was suitable for comparative dose-response studies of PGA₂, PGE₁ and PGE₂ and their analogs.     

Utility of d4-PGE2 as an internal standard to quantify endogenous levels of PGE1, PGE2, 190H PGE1 and 190H PGE2 in human seminal fluid by GC-MS-SIM

Four prostaglandins-PGE₁, PGE₂, 190H PGE₁ and 190H PGE₂-were quantified in human seminal fluid by GC-MS-SIM using only the internal standard, d₄-PGE₂. Methods and calculations were developed to minize errors inherent in using only one internal standard for quantifying four closely related prostaglandins. Preliminary data concerning the statistical significance of the differences found between PGE and 190H PGE levels in fertile, azospermic and oligospermic men are reported.     

Effects of PGE1 or PGE2 on luteal function in pseudopregnant rats

Effects of PGE₁ or PGE₂ on luteal function were studied in 163 pseudopregnant rats. PGE₁ (10, 100, or 300μg) given intrauterine every 6 hr did not shorten pseudopregnancy (P < 0.05), however, the same doses of PGE₂ given intrauterine every 6 hr advanced luteolysis (P < 0.05). PGE₁ (100 or 300μg) given every 4 hr intramuscular maintained levels of progesterone in peripheral blood above controls (P < 0.05) while 100 or 300μg of PGE₂ hastened the decline in progesterone (P < 0.05). The antiluteolytic effect of PGE₁ was not via an inhibition of PGF secretion (P < 0.05) by the uterus or by induction of ovulation in treated animals. Moreover, PGE₁ (100, 200, or 500μg) given intramuscular every 4 hr from day 4 of pseudopregnancy until the next proestrus delayed luteal regression around 3 days (P < 0.05). PGE₂ at doses of 100, 200, or 500μg every 4 hr given intramuscular consistently shortened pseudopregnancy (P < 0.05). Lower doses were without effect (P < 0.05). Based on the above data it is concluded that PGE₂ is consistently luteolytic whereas PGE₁ is not luteolytic in pseudopregnant rats and that PGE₁ may be an antiluteolysin.     

A specific radioimmunoassay for PGE2 using an antibody with high specificity and a sephadex LH-20 microcolumn for the separation of prostaglandins

Antiserum against PGE₂ was raised in rabbits following immunization with prostaglandin-hen-γ-globulin conjugate. The antiserum exhibited 14% cross reactivity with PGE₁ and far less cross-reaction with heterologous prostaglandins. A microcolumn of Sephadex LH-20 was used for a partial, but sufficient separation of PGE₂ from PGE₁ and a complete separation from heterologous prostaglandins to ensure a specific RIA for PGE₂. The precision of the method in the range 10–500 picograms showed a coefficient of variation varying between 4 and 13%. The detection limit was 10 picograms corresponding to 15 pg/ml of PGE₂ in serum.In order to demonstrate the validity of the method values obtained for non-diuretic rat renal venous serum were compared with those obtained using the isotope derivative method of Bojesen & Buckhave (1972) on the same samples. The concentrations of PGE₂ obtained were 239 ± 25 pg/ml and 250 ± 58 pg/ml, respectively.     

The effects of prostaglandins PGE1, PGE2, PGF1a, and PGF2a on canine synovial perfusion

In these experiments we have examined the effects of PGE₁, PGE₂, PGF_1α and PGF_2α on synovial perfusion in the normal canine synovial microcirculation. The effects of the drugs on synovial perfusion were determined indirectly from the changes produced in the rate of clearance of ¹³³Xenon from the joint by their intra-articular injection. Prostaglandins PGE₁ and PGE₂ were found to be strongly vasodilator with PGE₁ being the more active. PGF_1α appeared to have little or no vasoactive properties in doses up to 1 ugm. (2.8 × 10^−5M) in our I preparation while PGF_2α was vasodilator at this high dosage only. Neither SC19920 nor diphloretin phosphate antagonised the effects of PGE₁ in these experiments.     

Basal level of human platelet prostaglandins: PGE1 is more elevated than PGE2

Radioimmunoassays of platelet prostaglandins E₁ and F_1α in platelet rich plasma or platelet suspension, demonstrate that both PGE₁ and PGF_1α are present at higher concentrations than prostaglandins E₂ and F_2α. Gas chromatography — mass spectrometry determinations of prostaglandins E₁ and E₂ in resting washed platelets confirm this difference. Lastly, there is a greater incorporation of [1-¹⁴C] acetate into prostaglandins E₁ and F_1α compared to that into prostaglandins E₂ and F_2α.     

Inotropic effect of PGE1 and PGE2 on isolated rat atria. Influence of adrenergic mechanisms

The effects of a wide range of PGE₁ and PGE₂ concentrations on the isometric developed tension of isolated rat atria beating spontaneously or paced at a fixed rate, were explored. PGE₁ only produced a negative inotropic effect (NIE), whereas PGE₂ elicited a biphasic inotropic action; negative at low concentrations and positive (PIE) at higher ones. Phenoxybenzamine and phentolamine failed to modify either the NIE or the PIE, but subthreshold exogenous norepinephrine abolished the NIE, suggesting a presynaptic inhibitory effect of PGEs on the adrenergic neurotransmitter release. Auricles pretreated with subthreshold norepinephrine react with a PIE to PGE₁, but not to PGE₂. On the contrary in the presence of subthreshold methoxamine the PIE of PGE₂ was increased whereas the action of PGE₁ was not modified.     

Receptor binding in various tissues of PGE2, PGF2α and sulprostone, a novel PGE2-derivative

Sulprostone is a tissue-specific PGE₂-derivative with high abortifacient activity in various species including man. The dissociation constant K_D of the receptor binding of this compound was compared with PGE₂ and PGF_2α in various tissue preparations of different species. A structure-binding relationship was developed from competition curves after a logit/log transformation. It is demonstrated that the relative affinities of Sulprostone, PGE₂ and PGF_2α remain essentially constant in all the tissues investigated. It is concluded that the tissue-specificity of Sulprostone cannot be ascribed to structural differences of the receptor molecule.     

The effects of PGF1α, PGE2 and 16,16 dimethyl PGE2 on gastric emptying and small intestinal transit in rat

Prostaglandins are well known for their ability to stimulate contraction in gastrointestinal smooth muscle, yet very little information is available on how their activity affects propulsion . Thus, studies were undertaken to determine the effect of various prostaglandins on qastric emptying (GE) and small intestinal transit (SIT) in unanesthetized fasted rats. Rats were treated with intravenous, subcutaneous, or oral PGF_2α, PGE₂, or 16,16 dimethyl PGE₂ at various doses, followed 1 (intravenous), 20 (subcutaneous) or 10 (oral) mins later by intragastric ⁵¹Cr oxide in black ink. Forty-five mins later, rats were sacrificed by CO₂ asphyxiation, the pylorus clamped, and the gut excised. SIT was expressed as the percent of intestinal length traveled by the most distal portion of ink. GE was expressed as the percent of the ⁵¹Cr emptied into the intestines. If GE was affected by prostaglandin treatment, the experiments were repeated with rats pre-implanted with duodenal cannula. This preparation allowed the visual transit marker to be deposited directly into the dueodenum, thus avoiding acceleration or delay of SIT caused by fluctuations in GE. The results of these studies show that: (1) intravenous 16,16 dimethyl PGE₂ (5–50 μg/kg), but not PGF_2α or PGE₂, accelerates GE and delays SIT; (2) oral prostaglandin administration increases SIT; (3) oral 16,16 dimethyl PGE₂ delays GE; (4) subcutaneous 16,16 dimethyl PGE₂ accelerates, has no effect upon, or delays GE depending upon dose, but accelerates SIT at all doses tested; and (5) subcutaneous PGE₂ accelerates SIT while PGF_2α does not. Thus, the effect of prostaglandins on GE and SIT depends upon the dosage and route of administration as well as type of prostaglandin used.     

Prostaglandin E1 or E2 (PGE1, PGE2) prevents premature luteolysis induced by progesterone given early in the estrous cycle in ewes

The objective of this study was to determine whether prostaglandin E₁ (PGE₁) or prostaglandin E₂ (PGE₂) prevents premature luteolysis in ewes when progesterone is given during the first 6 days of the estrous cycle. Progesterone (3 mg in oil, im) given twice daily from Days 1 to 6 (estrus = Day 0) in ewes decreased (P < 0.05) luteal weights on Day 10 postestrus. Plasma progesterone concentrations differed (P < 0.05) among the treatment groups; toward the end of the experimental period, concentrations in jugular venous blood decreased (P < 0.05) compared with the other treatment groups. Plasma progesterone concentrations in ewes receiving PGE₁ or PGE₁ + progesterone were greater (P < 0.05) than in vehicle controls or in ewes receiving PGE₂ or PGE₂ or PGE₂ + progesterone. Chronic intrauterine treatment with PGE₁ or PGE₂ prevented (P < 0.05) decreases in plasma progesterone concentrations, luteal weights, and the proportion of luteal unoccupied and occupied LH receptors on Day 10 postestrus in ewes given exogenous progesterone, but did not affect (P > 0.05) concentrations of PGF_2α in inferior vena cava blood. Progesterone given on Days 1 to 6 in ewes advanced (P < 0.05) increases in PGF_2α in inferior vena cava blood. We concluded that PGE₁ or PGE₂ prevented progesterone-induced premature luteolysis by suppressing loss of luteal LH receptors (both unoccupied and occupied).     

Circulating and urinary metabolites of PGE2 and PGF2a

Fig. 1 summarizes the structures of primary PGE₂ and PGF_2a (upper line), their initially formed 15-ketodihydro-metabolites which appera early in blood after release (middle), and their β- and ω-oxidized metabolites, which appear later and remain longer in the circulation and also dominate the urinary profile (lower line). No single compound can be put forward as the ideal assay parameter: depending on aim and design of the study, either of these compounds may be monitored. The chemical instability of PGE compounds should however be kept in mind: generally it is safer to induce degradation by alkali treatment into a stable product prior to assay.     

Plasma levels of 13,14-dihydro-15-keto PGE2 after vaginal application of a new PGE2 film

To determine the release and absorption profile of prostaglandin E₂ from a new vaginal film formulation containing 850 μg PGE₂, serial plasma levels of 13,14-dihydro-15-keto PGE₂ were measured by radioimmunoassay in pregnant women between 16 and 18 weeks gestation. A control group, using placebo vaginal film was included in the study. There was a somewhat uniform increase in the plasma levels of the PGE₂ metabolite, reaching peak levels between 4 and 6 hours after application of the film. The findings suggest that this drug formulation could be used clinically when slow constant release of the prostaglandin is required over a period of hours such as in pre-induction cervical ripening of term pregnancy.     

PGE2 and PGF2α release by human peritoneal macrophages in endometriosis

Objective: To test for differences in the amount and activity of peritoneal macrophages present in the peritoneal fluid of women with, and without endometriosis using prostaglandin release by macrophages in culture as a marker.Patients: Women of reproductive age undergoing laparoscopy for infertility or chronic pelvic pain with postoperative diagnosis of endometriosis and women undergoing laparoscopy for sterilization.Methods: Peritoneal fluid was aspirated during laparoscopy, volume was recorded, macrophages were isolated via a Ficoll Paque gradient and kept in primary culture. PGE₂ and PGF_2α release of the cells were measured before and after stimulation with zymosan.Results: Women with endometriosis had significantly more peritoneal macrophages than controls. Peritoneal macrophages of women with endometriosis released significantly more PGE₂ than those of the control group: 8.4 ± 2.0 versus 1.4 ± 0.4 ng/ml/10⁶cells (mean ± SEM, p=0.0005) and PGF_2α : 10 ± 4.3 (endometriosis) versus 1.8 ± 0.4 (control) ng/ml/10⁶cells (mean ± SEM, p = 0.045).Conclusion: There is a significant increase in the amount of prostaglandins released by peritoneal macrophages from women with endometriosis. These prostaglandins might alter uterine and tubal contractility, thereby affecting fertility.     

Synthesis of two PGE2 human urinary metabolites

A synthesis (+) and (−) 7-α-hydroxy-5,11-diketo-tetranor prostanoic acid (Ia) and 7-α-hydroxy-5,11-diketotetranor prostan-1,16-dioic acid (Ib) is described. The biological activities of these C₁₆ metabolites are also discussed.     

Separation of thearubigins on sephadex LH-20

The nature of the peaks eluted from Sephadex LH-20 using aqueous acetone as eluent, from whole tea brews and various ethyl acetate-soluble thearubigin fractions, were examined. Monitoring the columns at 380 nm revealed two extra peaks compared to monitoring at 460 nm, and these were attributed to the presence of two pairs of flavonol glycosides. Sharp peaks which occurred at 2.6 V₀ with 60 % aqueous acetone as solvent were attributed to the action of inorganic ions contained in the samples under investigation. These, and other anomalous effects, were suppressed by electrolyte-containing eluents.     

PGE1 metabolism by the perfused rat liver

The hepatic and biliary metabolites of PGE₁ have been isolated and identified after infusions of PGE₁ into isolated rat liver preparations. The results demonstrate that in general PGE₁ undergoes metabolism similar to that of PGE₂ in the rat and reveals the possibility of a selective PG metabolite transport system across the biliary canalicular membrane.     

Dose response relation of the renal effects of PGA1, PGE2, and PGF2α in dogs

The effects of the three prostaglandins A₁, E₂, and F_2α on renal blood flow, glomerular filtration rate (GFR), fluid excretion, and urinary output of Na, K, Ca, Cl, and solutes were evaluated at a dose range of 0.01 – 10 μg/min. The prostaglandins were infused into the renal artery of dogs. GFR was not significantly altered by the PGs. PGA₁ increased renal blood flow by approximately of the control at 0.01 μg/min without dose dependence at higher infusion rates. It had only little effects which were not dose dependent on fluid and electrolyte output. The effects of PGE₂ on renal blood flow, fluid, sodium, and chloride excretion were dose dependent with a steep slope of the dose response curve between 0.1 and 1.0 μg/min. Blood flow was increased maximally by 80 %, urine volume by more than 400 %. PGF_2α had no effect on renal blood flow, whereas urinary output was increased to approximately the same maximal level as by E₂ although ten times higher doses were needed. Potassium excretion was less influenced than the excretion of Na and Cl and osmolar clearance was less increased than urine volume by all three prostaglandins.It is concluded that if a PG is involved in the regulation of the renal fluid or electrolyte excretion it is likely to be of the PGE-type. A PGA could only be involved in regulation of renal hemodynamics, whereas PGF although effective in the kidney exerts its effects at doses too high to have physiological significance.