Biological activity and anti-prostaglandin effects of prostaglandin analogue, ent-11-epi-15-epi PGE2 methyl ester

The biological activity and anti-prostaglandin property of the prostaglandin analogue, ent-11-epi-15-epi PGE2 methyl ester, were studied on isolated guinea pig ileum. Ent-11-epi-15-epi PGE2 methyl ester contracted guinea pig ileum and produced a concentration-response curve parallel to that of PGE2. However, the former exhibited a lower maximal effect than PGE2. At concentrations greater than 10(-6)M, ent-11-epi-15-epi PGE2 methyl ester selectively antagonized contractile actions of PGE2 and PGE2 alpha without affecting contractions induced by acetylcholine. These observations suggest that the PG analogue acted like a competitive antagonist to PGE2 and PGF2 alpha on guinea pig ileum in vitro.     

Has cervical smooth muscle any physiological role in the human?

Strips of human cervical tissue were obtained by needle biopsy and contractile activity was registered isometrically in a tissue chamber perfused by Krebs-Ringer bicarbonate buffer. The most frequently encountered pattern of contractile activity was high frequency-short duration. Prostaglandin (PG)E2, PGI2 and 6-keto-PGF1 alpha had an inhibitory effect on the muscular activity. Cervical muscle from pregnant women was more sensitive to PGE2 than specimens from non-pregnant women. PGF2 alpha had no apparent effect on cervical contractility in non-pregnant and early pregnant patients. In late pregnancy, however, PGF2 alpha inhibited muscle contractions. The present results point to a physiological role of the cervical muscles for the control of cervical competence during pregnancy. The inhibitory effect of PGs on the muscle activity may promote cervical dilatation and retraction.     

Cardiac effects of prostaglandins E1 and F1 alpha

The effects of prostaglandin E1 (PGE1) and prostaglandin F1 alpha (PGF1 alpha) were studied on perfused rat hearts and isolated rat atria. Both PGE1 and PGF1 alpha produced dose-dependent increases in right atrial rate but had no effect on left atrial tension development. PGE1 (10(-4) M) increased right atrial cyclic AMP content without changing phosphorylase a activity. PGF1 alpha (10(-4) M) did not change right atrial cyclic AMP or cyclic GMP content. Both prostaglandins had no effect on left atrial cyclic nucleotide content. When infused at a rate of 1 microgram/min, PGE1 produced a time-dependent increase in cyclic AMP content in the Langendorff perfused hearts but did not alter contractile force development or phosphorylase a activity. An infusion of PGF1 alpha produced a dose-dependent increase in tension development which was secondary to a negative chronotropic effect. PGF1 alpha (1 microgram/min) did not produce any changes in cyclic nucleotide levels or phosphorylase a activity in the Langendorff perfused hearts. These results show that PGE1 can selectively increase myocardial cyclic AMP content without altering contractile force or phosphorylase activity and that PGF1 alpha does not increase rat cardiac AMP levels.     

Is the epithelium-derived inhibitory factor in guinea-pig trachea a prostanoid?

To examine further the possible prostanoid involvement in the influence of the epithelium on guinea-pig tracheal smooth muscle responsiveness, we have analyzed the effects of LTD4, methacholine and histamine on the level of airway smooth muscle tone and on the amounts of PGE2, PGF2 alpha and PGI2 (determined by radioimmunoassay) in the presence and absence of the epithelium. Removal of the epithelium increased the sensitivity of guinea-pig trachea to the contractile effects of LTD4, methacholine and histamine. LTD4 (3-100 nM), methacholine (0.1-10 microM) or histamine (0.3-30 microM) did not increase prostanoid release above control values in either the presence or absence of the epithelium. The unstimulated release of PGE2 and PGF2 alpha, but not PGI2, was decreased in tissues lacking epithelium. Indomethacin (1 microM) reduced the baseline tone to a smaller extent in the absence of epithelium. In the presence but not the absence of the epithelium, indomethacin increased the sensitivity of preparations to the contractile effect of methacholine. The results support the postulate of an epithelium-derived inhibitory factor modulating guinea-pig tracheal smooth muscle responsiveness. The identity of this factor is not known but is not PGI2 and is unlikely to be PGF2 alpha or PGE2. However, the possibility remains that the basal release of PGE2 and/or PGF2 alpha derived from the epithelium may markedly affect the responsiveness of guinea-pig tracheal smooth muscle. Furthermore, the epithelium is a significant source of PGE2 and PGF2 alpha which may be involved in the maintenance of baseline tone.     

The effects of prostacyclin (PGI2) on tissues which detect prostaglandins (PG'S).

The effects of prostacyclin (PGI2) and its stable metabolite 6-oxo-PGF1alpha on various bioassay tissues are compared with those of PGE2 and PGF2alpha, using the cascade superfusion method. On vascular smooth muscle, PGI2 caused relaxation of all tissues tested except the rabbit aorta. PGE2 relaxed rabbit coeliac and mesenteric artery but contracted bovine coronary artery and had no effect on rabbit aorta. 6-oxo-PGF1alpha was ineffective at the concentrations tested. On gastro-intestinal smooth muscle, PGI2 contracted strips of rat and hamster stomach and the chick rectum. It was less potent than PGE2 or PGF2alpha. None of these substances contracted the cat terminal ileum. 6-oxo-PGF1alpha was inactive on these tissues at the doses tested. PGI2 was less active than PGE2 or PGF2alpha in contracting guinea-pig trachea and rat uterus; 6-oxo-PGF1alpha was active only on the rat uterus. Thus, PGI2 can be distinguished from the other stable prostaglandins using the cascade method of superfusion.     

Actions of prostaglandins E1 and F2alpha on isolated intrapulmonary vascular smooth muscle.

The effects of PGE1 and PGF2alpha were studied on isolated strips of intrapulmonary arteries and veins from dog, sheep, swine and man. PGF2alpha contracted human arterial strips in a dose-dependent fashion, relaxed slightly sheep arteries and had no effect on dog arteries. Canine, sheep and human venous strips were contracted by PGF2alpha. PGE1 relaxed slightly both veins and arteries from dog and sheep. Human arteries usually contracted slightly and human veins usually relaxed slightly to PGE1. In a limited number of experiments, swine arteries and veins failed to respond to PGF2alpha or PGE1. All the vascular strips contracted well when exposed to NE. These results suggest that the responses of intrapulmonary vessels to PGF2alpha and PGE1 are species-dependent. PGF2alpha generally exhibits a contractile action, especially on veins. PGE1 usually relaxes intrapulmonary vessels. With regard to vessels from man, PGF2alpha is a powerful stimulant while PGE1 produces only small, variable effects.     

Effect of polyphloretin phosphate on the response of non-gravid rat uterus to folkloric and standard oxytocics in vitro

Polyphloretin phosphate (PPP) has been reported by previous workers to be a specific antagonist of prostaglandin (PGE(1), PGE(2) & PGF(2 alpha))-induced contractions of isolated jird colon, gerbil colon, guinea pig ileum, and rabbit jejunum. In the present study, we examined the effect of PPP on uterotonic activities of crude papaya latex (a folkloric oxytocic), PGF(2 alpha), oxytocin, acetylcholine, and 5-hydroxytryptamine (standard oxytocics) on non-gravid, oestrogen-primed (50 microg/kg) rats in vitro. The effect of PPP on the oxytocics was evaluated qualitatively by incubating the tissues in PPP (25 - 400 microg/ml) for 20 min prior to the addition of a constant concentration of each oxytocic. PPP concentration dependently inhibited the contractile response of the uterine muscles to all the oxytocics. The inhibition was reversible after washing out the drugs. Results of the present study suggest that PPP is a non-specific and reversible antagonist of the response of non-gravid rat uterine smooth muscle to oxytocics in vitro. The specificity of PPP as a prostaglandin antagonist could therefore be species/tissue dependent.     

Prostacyclin induces a surprising long-lasting motility in quiescent uterine strips (indomethacin-treated) isolated from ovariectomized rats

Dose-response curves for several prostaglandins (PGI2; PGD2; PGF2 and PGE2); BaCl2 or prostaglandin metabolites (15-keto-PGF2 alpha; 13,14-diOH-15-keto-PGF2 alpha; 6-keto-PGF1 alpha and 6-keto PGE1 in quiescent (indomethacin-treated) uterine strips from ovariectomized rats, were constructed. All PGs tested as well as BaCl2, triggered at different concentrations, evident phasic contractions. Within the range of concentrations tested the portion of the curves for the metabolites of PGF2 alpha was shifted to the right of that for PGF2 alpha itself; the curve for 6-keto-PGF1 alpha was displaced to the right of the curve for PGI2 and that for 6-keto-PGE1 to the left. It was also demonstrated that the uterine motility elicited by 10(-5) M PGF2 alpha and its metabolites was long lasting (more than 3 hours) and so it was the activity evoked by PGI2;6-keto-PGF1 alpha and BaCl2, but not the contractions following 6-keto-PGE1, which disappeared much earlier. The contractile tension after PGF2 alpha; 15-keto-PGF2 alpha; 13,14-diOH-15-keto-PGF2 alpha and PGI2, increased as time progressed whilst that evoked by 6-keto-PGF1 alpha or BaCl2 fluctuated during the same period around more constant levels. The surprising sustained and gradually increasing contractile activity after a single dose of an unstable prostaglandin such as PGI2, on the isolated rat uterus rendered quiescent by indomethacin, is discussed in terms of an effect associated to its transformation into more stable metabolites (6-keto-PGF1 alpha, or another not tested) or as a consequence of a factor which might protects prostacyclin from inactivation.     

On the mechanism of action of 15-methyl-PGF2 alpha as an abortifacient.

Several hours following administration of long acting vaginal suppositories containing 3.0 mg of 15-methyl-PGF2 alpha for interruption of second trimester pregnancies there is an up to 10-fold increase in endogenous production of PGE2 and PGF2 alpha before abortion as reflected by gas chromatographic-mass spectrometric determination of the major plasma metabolites of PGE2 and PGF2 alpha. The data suggest that this increased formation of endogenous prostaglandins contributes to the induced uterine activity during the latter part of the abortion process.     

The actions of prostaglandins and cyclo-oxygenase inhibition on the resistance vessels supplying the human fetal placenta

The resistance arteries supplying individual exchange villi of the full-term human fetal placenta were examined for their reactivity to various prostaglandins (PG's) as well as for their ability to synthesize biologically active PG's. PGA1, PGF2 alpha, PGE2 and PGE1 produced dose-dependent contractions between 10(-7) and 10(-5)M. The order of potency observed was PGA1 approximately PGF2 alpha greater than PGE2 greater than PGE1. TXB2 was without activity in this preparation. Prostacyclin (PGI2) produced a dose-dependent relaxation of pre-contracted strips between 10(-8)M and 10(-5)M. Arachidonic acid (A.A.) produced stable dose-dependent contractions (10(-5) M to 10(-3)M) which were totally abolished by pretreatment with 10(-7)M meclofenamate (MF). At no concentration of A.A. was any evidence of vascular relaxation observed. Larger concentrations of MF (greater than 10(-6)M) resulted in a non-specific depression of the placental vascular smooth muscle. Meclofenamate (10(-7)M) pretreatment of strips subjected to dose-response studies using PGF2 alpha, PGE2, bradykinin (B K) and angiotensin II (AII) revealed a significant reduction in tension developed to both BK and AII. This finding suggests that the vasoactive peptides BK and AII stimulate the synthesis of vasoconstricting PG's in the fetal placental resistance arteries which relax in response to PGI2 and contract in response to the other PG's tested.     

Influence of 15-keto-metabolites and 13,14-dihydro-15-keto-metabolites of PGE2 and PGF2 alpha as well as of 6-keto-PGF1 alpha as a metabolite of PGI2 on aconitine induced cardiac arrhythmia in rats

The 15-keto-metabolites of PGE2 and PGF2 alpha produced an antiarrhythmic effect on aconitine induced arrhythmias in rats. The ED50 values of these metabolites were approximately 2.0 micrograms/kg. The 13,14-dihydro-15-keto-metabolites of PGE2 and PGF2 alpha had no statistically significant antiarrhythmic effect. PGI2 (0.25-1.00 micrograms/kg) produced an antiarrhythmic effect between 15-54% (ED50 0.75 micrograms/kg), whereas 6-keto-PGF1 alpha, a metabolite of PGI2, showed no significant antiarrhythmic effect. The results suggest a participation of 15-keto-metabolites in the antiarrhythmic effects of PGE2 and PGF2 alpha.     

Prostaglandin release from the guinea-pig uterus superfused in vitro. Effect of stage of estrous cycle, progesterone, estradiol, oxytocin and A23187

Prostaglandin (PG) E2 was the major PG released from the superfused guinea-pig uterus on Day 7, followed by in descending order 6-oxo-PGF1 alpha, thromboxane (TX) B2 and PGF2 alpha. However, the outputs of all four substances were low and were very similar. By Day 15, PGF2 alpha output from the superfused uterus had increased 21.9-fold, whereas the outputs of PGE2, 6-oxo-PGF1 alpha and TXB2 had increased only 1.8-, 2.9- and 1.2-fold, respectively. A mechanism is apparently "switched on" between Days 7 and 15 which causes a fairly specific increase in the release of PGF2 alpha from the uterus. Progesterone and/or estradiol had no effect on PG or TX release when superfused over the uterus on Day 7, nor did they have any effect on PG and TX release from the Day 15 uterus when administered separately. When administered together, however, they significantly inhibited PGF2 alpha, PGE2 and 6-oxo-PGF1 alpha, but not TXB2, release from the Day 15 uterus. Oxytocin had no effect on PG release from the Day 7 or Day 15 uterus, while A23187 stimulated PGF2 alpha, 6-oxo-PGF1 alpha and, to a lesser extent, PGE2 release from the uterus on both Days 7 and 15. Oxytocin is apparently not important for stimulating PGF2 alpha release from the guinea-pig uterus in relation to luteolysis, whereas increasing intracellular free Ca++ levels may be part of the mechanism for "switching on" uterine PG synthesis. Furthermore, changes in intracellular free Ca++ levels in the endometrium may be responsible for the pulsatile nature of PGF2 alpha release from the uterus.     

Phorbol ester stimulates cyclooxygenase-2 expression and prostanoid production in cardiac myocytes

Phorbol-12-myristate- 13-acetate (PMA) has been shown to induce hypertrophy of cardiac myocytes. The prostaglandin endoperoxide H synthase isoform 2 (cyclooxygenase-2, COX-2) has been associated with enhanced growth and/or proliferation of several types of cells. Thus we studied whether PMA induces COX-2 and prostanoid products PGE(2) and PGF(2alpha) in neonatal ventricular myocytes and whether endogenous COX-2 products participate in their growth. In addition, we examined whether PMA affects interleukin-1beta (IL-1beta) stimulation of COX-2 and PGE(2) production. PMA (0.1 micromol/l) stimulated growth, as indicated by a 1.6-fold increase in [(3)H]leucine incorporation. PMA increased COX-2 protein levels 2. 8-fold, PGE(2) 3.7-fold, and PGF(2alpha) 2.9-fold. Inhibition of either p38 kinase or protein kinase C (PKC) prevented PMA-stimulated COX-2. Inhibition of COX-2 with either indomethacin or NS-398 had no effect on PMA-stimulated [(3)H]leucine incorporation. Exogenous administration of PGF(2alpha), but not PGE(2), stimulated protein synthesis. Treatment with IL-1beta (5 ng/ml) increased COX-2 protein levels 42-fold, whereas cotreatment with IL-1beta and PMA stimulated COX-2 protein only 32-fold. IL-1beta did not affect control or PMA-stimulated protein synthesis. These findings indicate that: 1) PMA, acting through PKC and p38 kinase, enhances COX-2 expression, but chronic treatment with PMA partially inhibits IL-1beta stimulation of COX-2; and 2) exogenous PGF(2alpha) is involved in neonatal ventricular myocyte growth but endogenous COX-2 products are not.     

Effect of PGF2 alpha and 15(S)-15-methyl PGE2 methyl ester on feline generalized penicillin epilepsy.

The effect of PGF2alpha and 15(S)-15-methyl PGE2 methyl ester on transient generalized epilepsy in the cat induced by penicillin was examined. Epileptic activity before and after administration of the prostaglandins by several routes was determined from continuous EEG recordings and expressed in epileptic bursts per min. The PGE2 analogue given in single non-toxic doses (1.6-3 mug/kg) by intramuscular or intravenous routes at the peak of epileptic activity significantly reduced epileptic activity for up to four hours. Subcutaneous administration was less effective. PG2alpha given by the intramuscular route (0.3 mg/kg) also markedly reduced the number of epileptic bursts. Increasing the dosage 4-fold almost completely suppressed epileptic activity. Intracarotid infusion of PGF2alpha for one hour (10 mug/min) almost abolished all epileptic activity. Neither prostaglandin given in non-toxic doses induced EEG abnormalities in non-epileptic cats. Toxic doses of the E2 analogue (greater than 16 mug/kg) caused bilaterally synchronous high voltage slow wave activity. It is concluded that these prostaglandins reduce penicillin epilepsy in the cat. The findings are consistent with either a direct excitatory action on neurones of the medial reticular formation or anatagonism of the depressant action of norepinephrine on Purkinje cells.     

Dissociation of the contractile and hypertrophic effects of vasoconstrictor prostanoids in vascular smooth muscle.

To more clearly define the physiologic roles of thromboxane (TX)A2 and primary prostaglandins (PG) in vascular tissue we examined vascular contractility, cell signaling, and growth responses. The growth-promoting effects of (15S)-hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5Z,13E-dienoic acid (U46619; TXA2 agonist), PGF2 alpha, and PGE2 consisted of protein synthesis and proto-oncogene expression, but not DNA synthesis or cell proliferation. U46619 contracted rat aortas and increased cultured rat aortic vascular smooth muscle cell intracellular free calcium concentration [Ca2+]i, [3H]inositol monophosphate (IP) accumulation, myosin light chain phosphorylation, and protein synthesis ([3H]leucine incorporation) with EC50 values ranging from 10 to 50 nM. Each of these responses was inhibitable with the TXA2 receptor antagonist [1S]1 alpha,2 beta(5Z),3 beta,4 alpha-7-(3-[2- [(phenylamino)carbonyl]hydrazino]methyl)-7-oxabicyclo[2.2.1]hept-2- yl-5-heptenoic acid (SQ29548). In contrast, PGF2 alpha increased [Ca2+]i, [3H]IP, and protein synthesis with EC50 values of 30-230 nM but contracted rat aortas with an EC50 of 4800 nM. PGE2 increased [Ca2+]i, [3H]IP accumulation, protein synthesis, and contracted rat aortas with EC50 values of 2.5-3.5 microM. TXA2 receptor blockade prevented PGF2 alpha- and PGE2-induced aortic contraction and cell myosin light chain phosphorylation, but not cell signaling or protein synthesis. Binding studies to vascular smooth muscle TXA2 receptors using 1S-[1 alpha,2 beta(5Z),3 alpha(1E,3S),4 alpha]-7-(3-[3-hydroxy-4-(p- [125I]iodophenoxy)-1-butenyl]7-oxabicyclo[2.2.1]hept-2-yl)-5-hepte noic acid ([125I]BOP) showed U46619, SQ29548, PGF2 alpha, and PGE2 competition for TXA2 receptor binding at concentrations similar to their EC50 values for aortic contraction, while binding competition with [3H]PGF2 alpha and [3H]PGE2 demonstrated the specificity of [125I]BOP and SQ29548 for TXA2 receptors. The results suggest that 1) PGF2 alpha- and E2-stimulated vessel contraction is due to cross-agonism at vascular TXA2 receptors; 2) PGF2 alpha stimulates TXA2 receptor-independent vascular smooth muscle protein synthesis at nanomolar concentrations, consistent with an interaction at its primary receptor; and 3) TXA2 is a potent stimulus for vascular smooth muscle contraction and protein synthesis. We suggest that the main physiologic effect of PGF2 alpha may be as a stimulus for vascular smooth muscle cell hypertrophy, not as a contractile agonist.     

Biophysical studies on molecular mechanism of abortifacient action of prostaglandins. VI. Conformation energy calculation on PGE2, PGF2 alpha and 15-(s)-methyl PGF2 alpha

This paper reports the conformation energy (CE) calculations on PGE2, PGE2 alpha and 15-(s)-methyl PGE2 alpha on the basis of empirical potential energy functions for the simultaneous rotations around C7-C8 (psi), C12-C13 (theta) and C14-C15 (phi) bonds. The variation of the minimum conformation energy E for each isoenergy map in the psi theta plane with respect to phi gives two minima around 90 degrees and 240 degrees in PGE2, 60 degrees and 245 degrees in PGF2 alpha, and 60 degrees and 150 degrees in 15-(s)-methyl PGF2 alpha. The latter two forms also have a small dip at 270 degrees. The pattern of allowed low energy conformations of PGF2 alpha and 15-(s)-methyl PGF2 alpha is quite similar and is characterized by the existence of six low energy regions.     

PGF2 alpha, PGE2, and sex steroids from the abdominal gland of the male crested newt Triturus carnifex (Laur.).

Prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 (PGE2), progesterone, androgens, and 17 beta-estradiol in vitro release by the abdominal gland of the crested newt, Triturus carnifex (Laur.), was studied during the prereproductive, reproductive and postreproductive periods. In addition, the in vitro effects of the PGF2 alpha and/or PGE2 on progesterone, androgens and estradiol release by the abdominal gland were evaluated. PGF2 alpha, PGE2 and progesterone release was higher during the reproductive period, and in the same period, PGE2 treatment induced a progesterone increase. PGF2 alpha induced an increase of abdominal gland estradiol release at the end of the reproductive period. These results seemed to confirm the pheromonal role assigned to progesterone, and suggested a PGE2 stimulatory role in inducing progesterone release, even if pheromonal activity of PGF2 alpha and PGE2 cannot be excluded. In addition, PGF2 alpha-dependent estradiol increase at the end of reproduction could be interpreted as a mechanism for interruption of the abdominal gland activity.     

Cerebrovascular effects of prostanoids: in-vitro studies in feline middle cerebral and basilar artery

The effect of prostaglandin (PG) E2, F2 alpha, the thromboxane-A2 mimetic U46619 (9,11-dideoxy-9 alpha,11 alpha-methanoepoxy-prostaglandin F2 alpha) and the prostacyclin mimetic iloprost was investigated in cat middle cerebral and basilar arteries in vitro precontracted with 5-hydroxytryptamine (5-HT) (50nM) in the absence and presence of the cyclooxygenase inhibitor indomethacin or the thromboxane receptor blocker AH23848B [1 alpha (z),2 beta,5 alpha]-(+)-7-[5-[1,1'-(biphenyl)-4-yl] methoxy]-2-(4-morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid). PGF2 alpha and U46619 both produced further concentration-related contractions of basilar and middle cerebral artery, U46619 being approximately 1,000 times more potent than PGF2 alpha. Iloprost produced concentration-related relaxations of precontracted basilar and middle cerebral artery, the mean maximum relaxations produced at a concentration of 1.3 microM being 57.3% and 80.6%, respectively of the contraction produced by 50nM 5-HT. PGE2, 100nM relaxed the basilar and middle cerebral artery, 46.7% and 38.5% respectively. However, at 1 microM, PGE2 caused contraction. Indomethacin, 2.8 microM had no effect on contractile or relaxant responses to any of the prostanoids. Oxyhaemoglobin inhibited the relaxation of both arterial preparations but had no effect on responses to PGE2 or iloprost. The thromboxane-receptor blocker AH23848B antagonised the contractile responses to U46619, PGF2 alpha and PGE2 and had no effect against relaxant responses to PGE2 or iloprost. It is concluded that both contraction- and relaxation-inducing prostanoid receptors are present in the in vitro preparation of feline basilar and middle cerebral artery. Under sustained tension conditions, endothelial factors do not appear to be involved in the responses to dilating prostanoids.     

Effects of prostaglandin E2 and F2 alpha on cytoplasmic pH in a clonal osteoblast-like cell line, MOB 3-4.

Prostaglandin E2 (PGE2, 5 ng/ml to 5 micrograms/ml) induced a dose-dependent increase in cAMP accumulation, inositol phosphates (IPs) accumulation, and cytoplasmic free Ca2+ ([Ca2+]i) in a clonal osteoblast-like cell line, MOB 3-4. In contrast, prostaglandin F2 alpha (PGF2 alpha, 5 ng/ml to 5 micrograms/ml) stimulated increases in IPs accumulation and [Ca2+]i without stimulating an increase in cAMP accumulation. Both PGE2 (greater than 0.5 micrograms/ml) and PGF2 alpha (greater than or equal to 5 micrograms/ml) increased cytoplasmic pH (pHi) from approximately 7.15 to 7.35 in BCECF-loaded cells. A tumor promotor, phorbol 12-myristate 13-acetate (PMA, 0.1-100 nM) also increased pHi without effect on phosphoinositide hydrolysis. Both PGE2-(5 micrograms/ml) and PMA- (100 nM) induced cytoplasmic alkalinization was inhibited by removal of extracellular Na+, or by pretreatment of the cells with amiloride (0.5 mM), an inhibitor of Na+/H+ exchange, or H-7 (100 microM), a nonspecific inhibitor of protein kinase C. Thus, MOB 3-4 cells appeared to possess PGE2 receptors and PGF2 alpha receptors: the former are coupled to adenylate cyclase and phospholipase C, and the latter are predominantly coupled to phospholipase C. Also the cells appeared to possess an amiloride-sensitive Na+/H+ exchange activity, which increases pHi in response to PGE2 and PGF2 alpha, as well as to PMA. Long-term (48 hr) exposure of the cells to PGE2 at a high concentration (5 micrograms/ml), but not to PGF2 alpha and PMA, decreased DNA synthesis in the serum-deficient medium. Thus, cytoplasmic alkalinization appeared insufficient for cell replication. At least in MOB 3-4 cells, the inhibitory effect of PGE2 on DNA synthesis may be due to the cAMP messenger system.     

Receptors for prostaglandins F2 alpha and E2 in ovine corpora lutea during maternal recognition of pregnancy.

Plasma membrane receptors for prostaglandins (PG) F2 alpha and E2 were quantified in ovine corpora lutea obtained from nonpregnant and pregnant ewes on Days 10, 13, and 15 post-estrus, and from additional ewes on Days 25 and 40 of pregnancy. Regardless of reproductive status or day post-estrus, concentrations of luteal receptors for PGF2 alpha were 7- to 10-fold greater than those for PGE2. In pregnant ewes the concentration of receptors for PGF2 alpha was highest on Day 10 (35.4 +/- 2.8 fmol/mg) and lowest on Day 25 (22.3 +/- 2.5 fmol/mg). A difference in the concentration of luteal receptors for PGF2 alpha between pregnant and nonpregnant ewes was apparent only on Day 15 post-estrus, at which time the concentration of receptors for PGF2 alpha was higher in pregnant ewes than in nonpregnant ewes (27.1 +/- 2.7 vs. 17.7 +/- 2.7 fmol/mg). Concentrations of receptors for PGE2 in pregnant ewes were similar (p > 0.05; 2.8 +/- 0.3 to 3.7 +/- 0.2 fmol/mg) between Days 13 and 40 but were higher (p < 0.05) than in corpora lutea obtained from nonpregnant ewes on Days 10 (5.0 +/- 0.4 vs. 4.1 +/- 0.2 fmol/mg) and 15 (3.7 +/- 0.2 vs. 2.0 +/- 0.4 fmol/mg) post-estrus. Although concentrations of receptors for both PGF2 alpha and PGE2 were lowest in corpora lutea obtained from nonpregnant ewes on Day 15, this was not due to luteal regression since the weights and concentrations of progesterone in corpora lutea on Day 15 were not lower than those for corpora lutea obtained on Days 10 and 13.(ABSTRACT TRUNCATED AT 250 WORDS)