Cardiovascular actions of prostaglandins F2α; 15-me-F2α; F1α; F2β and F1β in the cat

Prostaglandin F_2α (5μg/kg, i.v.) causes an increase in pulmonary arterial pressure, decrease in systemic arterial pressure, and reflex bradycardia in the anesthetized cat. The same dose of the 15-methyl analogue of PGF_2α produces the same triad of effects but of greater magnitude and duration. Although prostaglandins F_1α, F_2β and F_1β also cause the same cardiovascular effects as F_2α, there is a decrease in potency for all parameters measured, with PGF_2α>PGF_1α>PGF_2β>PGF_1β. When compared to the actions of PGF_2α in producing an increase in pulmonary arterial pressure, PGs F_1α, F_2β and F_1β were less potent by approximately 10, 100, and 1000 fold 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.     

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.     

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.     

Effect of PGI2, PGE2 and 6-keto PGF1α on canine gastric blood flow and acid secretion

Prostaglandins (PG)I₂, PGE₂ and 6-keto PGF₁α were infused directly into the gastric arterial supply at 10⁻⁹, 10⁻⁸ and 10⁻⁷ g/kg/min during an intra-gastric artery pentagastrin infusion in anesthetized dogs. 6-keto PGF₁α was also infused at 10⁻⁶ g/kg/min. Gastric arterial blood flow was measured continuously with a non-cannulating electromagnetic flow probe and gastric acid collected directly from the stomach. PGI₂ and PGE₂ produced similar dose-dependent increases in blood flow with an increase of more than four-fold at the highest dose. Both PGs inhibited acid output over this dose range with PGE₂ having 10 times the potency of PGI₂. 6-keto PGF₁α was at least 1000 times less active than PGI₂ or PGE₂ at increasing blood flow and failed to inhibit acid output even at 10⁻⁶ g/kg/min.     

Glycerolipid formation and PGE2 and PGF2α production of rat renal papillae in vitro, the effects of urea

The glycerolipid production by rat renal papillary slices varied inversely with the urea concentration (0a–1660 mM) whether the production was measured as labelling of the glycerol backbone from glucose or as incorporation of labelled arachidonic acid and palmitic acid. The rate of phospholipid formation was most dependent on medium urea concentrations in the range between 0 and 1100 mM. The production of prostaglandins PGE₂ and PGF_2α, measured radioimmunologically or by an isotope derivative method was in the same range inversely related to the production of glycerolipids and chain elongations. The effect of urea on prostaglandin formation is probably indirectly caused by the inhibition of the phospholipid formation and chain elongation, since the effect was abolished by 1% defatted albumin in the medium. The data suggest that the level of free arachidonic acid within the cells is controlled to an important extent by glycerolipid formation and chain elongation.     

Changes in the metabolism of PGE1 and PGF2α in rat placenta during pregnancy

The metabolism of PGE₁ and PGF_2α were studied in an in vitro system using placentae from 11-day pregnant rats. PGE₁ was metabolized faster than PGF_2α. The same system was employed to study the quantitative metabolism of these prostaglandins at various stages of pregnancy in the rat. Results of these investigations showed that metabolism became maximal between days 9–12 and between days 15–22 of gestation. On days 12–15 of pregnancy, metabolism decreased, and was at its lowest point on day 14. Maximum prostaglandin metabolism during the sensitive period of days 9–12 of gestation may act as a protective device against the detrimental effects of prostaglandin. Possible correlation of prostaglandin regulation with hormonal balance is discussed.     

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.     

Characterization and ontogeny of PGE2 and PGF2α receptors on the retinal vasculature of the pig

The vasoconstrictor effects of PGE₂ and PGF_2α are less pronounced on retinal vessels of the newborn than of the adult pig. We tested the hypothesis that the decreased vasomotor response to these prostaglandins might be due to relatively fewer receptors and/or different receptor subtypes (in the case of PGE₂) on retinal vessels of the newborn animal. Binding studies using [³H]PGE₂ and [³H]PGF_2α revealed that PGE₂ (EP) and PGF_2α (FP) receptor densities in retinal microvessel membrane preparations from newborn animals were approximately 25% of those found in vessels from the adult. The K_d for PGF_2α did not differ; however, the K_d for PGE₂ was less in newborn than in adult vessels. Competition binding studies using AH 6809 (EP₁ antagonist), butaprost (EP₂ agonist), M&B 28,767 (EP₃ agonist), and AH 23848B (EP₄ antagonist) suggested that the retinal vessels of the newborn contained approximately equal number of EP₁ and EP₂ receptor subtypes whereas the main receptor subtype in the adult vessels was EP₁. In addition, PGE₂ and butaprost produced comparable increases in adenosine 3′,5′-cyclic monophosphate synthesis in newborn and adult vessels. PGE₂, 17-phenyl trinor PGE₂ (EP₁agonist) and PGF_2α caused a 2.5 to 3-fold greater increase in inositol1,4,5-triphosphate (IP₃) formation in adult than in newborn preparations. It is concluded that fewer PGF_2α receptors and an associated decrease in receptor-coupled IP₃ formation in the retinal vessels of the newborn could lead to weaker vasoconstrictor effects of PGF_2α on retinal vessels of the newborn than of adult pigs; fewer EP₁ receptors (associated with vasoconstriction) and a relatively greater proportion of EP₂ receptors (associated with vasodilation) might be responsible for the reduced retinal vasoconstrictor effects of PGE₂ in the newborn.     

Facile method for preparation of 2,3-dinor-6-keto PGF1α, the major urinary metabolite of prostacyclin

We report a convenient and efficient method for the preparation of prostaglandin 2,3-dinor-6-keto-F_1α by incubating prostaglandin 6-keto-PGF_1α (6-keto-PGF_1α) with dispersed rat hepatocytes. Chromatographic separation revealed a single product from the hepatocyte metabolism of 6-keto-PGF_1α whose structure was positively confirmed by mass spectrometry as 2,3 dinor-6-keto-PGF_1α. This methods allowed for the preparation of high specific activity radioactive 2,3-dinor-6-keto-PGF_1α which can be utilized to determine the recovery of urinary dinor-6-keto-PGF_1α during extraction and separation of the compound for radioimmunoassay measurements, as well as deuterated 2,3-dinor-6-keto-PGF_1α which can be used as an internal standard in the gas chromatography-mass spectrometric assay of this compound.     

The effect of PGE2 and PGF2α on the response of guinea pig myometrium to adenine nucleotides in vitro

Prostaglandins E₂ and F_2α potentiate contractile effect induced by adenine nucleotides ATP, ADP and AMP in guinea pig myometrium in vitro. Prostaglandins and nucleotides were added to the organ bath in minute concentrations which have been proved ineffective or slightly contractile when both groups of substances were administered separately. The data of the present work, together with our previously published studies (9,10,13), where the action of exogenous adenine nucleotides, NAD and adenosine on rabbit's jejunum in vitro has been proved antagonistic to the contractile effect of various prostaglandins, suggest that prostaglandins and adenine nucleotides appear to block selectively or augment each other's action on various organs. The initial hypothesis that there is a regulatory correlation between endogenous prostaglandins and the function of purinergic nerves also is reinforced.     

Determination of 6-keto-PGF1α, 2,3-dinor-6-keto-PGF1α, thromboxane B2, 2,3-dinor-thromboxane B2, PGE2, PGD2 and PGF2α in human urine by gas chromatography—negative ion chemical ionization mass spectrometry

A method for quantification of 6-keto-PGF_1α, 2,3-dinor-6-keto-PGF_1α, TXB₂, 2,3-dinor TXB₂, PGE₂, PGD₂ and PGF_2α in human urine samples, using gas chromatography—negative ion chemical ionization mass spectrometry, is described. Deuterated analogues were used as internal standards. Methoximation was carried out in urine samples which were subsequently applied to phenylboronic acid cartridges, reversed-phase cartridges and thin-layer chromatography. The eluents were further derivatized to pentafluorobenzyl ester trimethylsilyl ethers for final quantification by gas chromatography—mass spectrometry. The overall recovery was 77% for tritiated 6-keto-PGF_1α and 55% for tritiated TXB₂. Urinary levels of prostanoids were determined in a group of six volunteers before and after intake of the thromboxane synthase inhibitor Ridogrel, and related to creatinine clearance.     

PGE2 attenuates PGF2α-induced increases in free intracellular calcium in ovine large luteal cells

When ovine large luteal cells are placed in culture and exposed to PGF_2α, there is a rapid and sustained increase in the concentration of free intracellular calcium which is believed to play a major role in the luteolytic and cytotoxic effects of PGF_2α. Since administration of exogenous PGE₂ can prevent spontaneous and PGF_2α-induced luteolysis in vivo, and the cytotoxic effects of PGF_2α on large luteal cells in vitro, the objective of this study was to determine if one mechanism by which PGE₂ acts is to attenuate increases in free intracellular calcium induced by PGF_2α. At concentrations of 10 nM or greater, PGF_2α caused a significant and sustained increase in free intracellular calcium in large luteal cells. Similarly, PGE₂ also induced increases in free intracellular calcium but required doses 20-fold greater than PGF_2α. When PGE₂ (1, 10 or 100 nM) was incubated with PGF_2α (100 nM) increases in free intracellular calcium induced by PGF_2α were attenuated (P<0.05) when measured 5 min, but not at 30 min, after initiation of treatment. The observed decrease in the concentration of free intracellular calcium at 5 min in response to PGF_2α was the result of fewer cells responding to PGF_2α. In addition, the concentrations of free intracellular calcium attained in the cells that did respond was reduced 25% compared to cells treated with PGF_2α alone. Thus, part of the luteal protective actions of PGE₂ appears to involve an inhibition of the early (5 min) increase in free intracellular calcium induced by PGF_2α.     

Interactions of prostaglandins with subpopulations of ovine luteal cells. II. Inhibitory effects of PGF2α and protection by PGE2

Purified preparations of ovine large luteal cells were utilized in a series of experiments to test the effects of prostaglandins (PG) E₂ abd F₂α on cell morphology, viability and secretion of progesterone. Luteal cells were allowed to attach to culture dishes overnight before experiments. In the first series of experiments incubation of large steroidogenic cells with PGF₂α for 6 hr resulted in morphological changes including a retraction of the cell cytoplasm and apparent extrusion of cytoplasmic components which became more pronounced after 12 hr. In a second series of experiments, PGF₂α decreased and PGE₂ increased progesterone accumulation in media after 6 hr when media were not replaced during the incubation period, while progesterone accumulation was not different than that observed in control dishes when both prostaglandins were present. Hourly replacement of the media negated the inhibitory effects of PGF₂α but had no effect on the stimulated secretion of progesterone induced by PGE₂. Finally, in incubations without media replacement, PGF₂α induced a dose-dependent decrease in progesterone accumulation while PGE₂ elicited a biphasic response with progesterone secretion increasing from 0.1 ng/ml to maximal levels at 10 ng/ml followed by a dose-dependent decrease at 100 and 1000 ng/ml. These data are compatible with the hypotheses that: 1) luteolysis is initiated, at least in part, by an action of PGF₂α on large luteal cells; and 2) the embryonic signal from the pregnant uterus which rescues the ovine corpus luteum may be PGE₂.     

The effects of 11-methyl 16,16 dimethyl prostaglandin E2 on canine gastric acid secretion

11-Methyl 16,16 Dimethyl Prostaglandin E₂ (TM-PGE₂) at peak effectiveness inhibited acid output stimulated submaximally by histamine in the dog by 95 and 84% when administered by the intravenous and oral routes, respectively. Inhibition of secretion was maintained for hours following intravenous administration while with the oral route, secretory inhibition was still present at the end of two hours after administration of the drug. The degree of inhibition of acid secretion caused by TM-PGE₂, its duration of action and the lack of side effects observed following administration of this drug makes it a suitable compound for evaluation as an anti-secretory agent in man.     

Prostaglandin F2α (PGF2α) and prolactin secretion in rats

Plasma prolactin and F-prostaglandins (PGF) were measured in anesthetized male Sprague-Dawley rats before and at 15, 30, 45 and 60 minutes following i.v. injection of either PGF_2α (4 mg/kg), chlorpromazine, 1 mg/kg or chlorpromazine (1 mg/kg) after pretreatment with i.p. indomethacin (2 mg/kg). Following PGF_2α administration, plasma prolactin levels increased significantly only at 15 and 30 minutes in spite of extremely high PGF levels throughout 60 minutes. Besides the expected rise in plasma prolactin, chlorpromazine caused a transient but statistically significant increase in PGF. Indomethacin blocked the chlorpromazine-induced PGF rise but not prolactin increase. Animals stressed with ether anesthesia showed elevation of plasma prolactin, which was not blocked by indomethacin although PGF concentration fell. These results indicate that PGF_2α can stimulate prolactin release. This effect does not appear to be physiologic since very high PGF levels are required. Furthermore, blockade of prostaglandin synthesis by indomethacin does not prevent the release of prolactin in response to chlorpromazine or stress. Our findings do not support a possible role of PGFs as intermediaries in prolactin release. However, it is possible that PGFs may work through other mechanisms not investigated in our study.     

Effects of PGF2α and PGF2α, 1–15 lactone on the corpus luteum and on early pregnancy in the rhesus monkey

The effects of prostaglandin (PG)F_2α and PGF_2α, 1–15 lactone were compared in luteal phase, non-pregnant and in early pregnant rhesus monkeys. Animals treated with either PG after pretreatment with human chorionic gonadotropin (hCG) had peripheral plasma progesterone concentrations that were not statistically different from those in animals treated with hCG and vehicle. However, menstrual cycle lengths in monkeys treated with PGF_2α, 1–15 lactone were significantly (P <0.02) shorter than those in vehicle treated animals. In the absence of hCG pretreatment, plasma progesterone concentrations were significantly (P <0.008) lower by the second day after the initial treatment with either PGF_2α or PGF_2α, 1–15 lactone than in vehicle treated monkeys. Menstrual cycle lengths in monkeys treated with either PG were significantly (P <0.04) shorter than those in animals treated with vehicle. There were no changes in plasma progesterone concentrations in early pregnant monkeys treated with PGF_2α, and pregnancy was not interrupted. In contrast, plasma progesterone declined and pregnancy was terminated in 5 of 6 early pregnant monkeys treated with PGF_2α, 1–15 lactone. These data indicate that PGF_2α, 1–15 lactone decreases menstrual cycle lengths in non-pregnant rhesus monkeys. More importantly, PGF_2α, 1–15 lactone terminates early pregnancy in the monkey at a dose which is less than an ineffective dose of PGF_2α.     

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.     

Phosphorylations of αA- and αB-crystallin

In addition to being refractive proteins in the vertebrate lens, the two α-crystallin polypeptides (αA and αB) are also molecular chaperones that can protect proteins from thermal aggregation. The αB-crystallin polypeptide, a functional member of the small heat shock family, is expressed in many tissues in a developmentally regulated fashion, is stress-inducible, and is overexpressed in many degenerative diseases and some tumors indicating that it plays multiple roles. One possible clue to α-crystallin functions is the fact that both polypeptides are phosphorylated on serine residues by cAMP-dependent and cAMP-independent mechanisms. The cAMP-independent pathway is an autophosphorylation that has been demonstrated in vitro, depends on magnesium and requires cleavage of ATP. Disaggregation of αA-, but not αB-crystallin into tetramers results in an appreciable increase in autophosphorylation activity, reminiscent of other heat shock proteins, and suggests the possibility that changes in the aggregation state of αA-crystallin are involved in yet undiscovered signal transduction pathways. The α-crystallin polypeptides differ with respect to their abilities to undergo cAMP-dependent phosphorylation, with preference given to the αB-crystallin chain. These differences and complexities in α-crystallin phosphorylations, coupled with the differences in expression patterns of the two α-crystallin polypeptides, are consistent with the idea that each polypeptide has distinctive structural and metabolic roles.     

The effects of 11-methyl 16,16 dimethyl prostaglandin E2 on gastric acid secretion in man

11-Methyl 16,16 Dimethyl Prostaglandin E₂ (TM-PGE) was administered orally to man in dosages of 2.5, 5, 7.5 and 10 μg/kg. Maximal inhibition of basal secretion was 52 and 78% and submaximal histamine-stimulated secretion 45 and 70% for volume and acid output, respectively. Secretory inhibition was observed for approximately two hours after ingestion of the drug. No effect was observed on serum gastrin levels. Side effects occurred with equal frequency in the placebo and drug groups. TM-PGE is well tolerated and inhibits both basal and submaximal histamine-stimulated acid secretion in man. Further evaluation may prove it to be helpful in the clinical treatment of acid hypersecretory states and peptic ulcer disease.