The dynamic content of prostaglandins and cyclic nucleotides in the blood of irradiated dogs and monkeys

In experiments with dogs and monkeys a study was made of the dynamics of the content of prostaglandins (PG) and cyclic nucleotides after gamma irradiation. In dogs irradiation with lethal doses (3.1 and 50 Gy) caused a short-term, evidently stress growth of cAMP, PGE and PGF2 alpha levels. At the height of radiation sickness PGF2 alpha and cGMP content decreased considerably. Irradiation of monkeys with a nonlethal dose of 3.2 Gy changed PGE and PGF2 alpha levels to a lesser extent, while concentrations of cyclic nucleotides varied but their ratio remained stable.     

Effect of prostaglandins on luteal function during early pregnancy in pigs.

Luteal cells were obtained by digestion of luteal tissue of cyclic (day 12) and early pregnant (days 12, 20 and 30) pigs. Suspensions of the dispersed luteal cells (5 x 10(4) cells ml-1) were incubated for 2 h in minimum essential medium (MEM) alone (control) and MEM with different concentrations of prostaglandin F2 alpha (PGF2 alpha) and PGE2 (0.01, 0.1, 1, 10, 100 and 1000 ng ml-1) and luteinizing hormone (LH) 100 and 1000 ng ml-1, or with combinations of LH + PGF2 alpha and LH + PGE2. Net progesterone production was measured in the incubation media by direct radioimmunoassay. The overall response pattern of the luteal cells to exogenous hormones on day 12 of the oestrous cycle and pregnancy differed (P < 0.05) from treatment on day 20 and 30 of pregnancy. In general progesterone production was higher (P < 0.05) and the response to PGF2 alpha and PGE2 treatment was most obvious on day 12 of the oestrous cycle and pregnancy. Overall, PGF2 alpha stimulated progesterone production in a dose-dependent manner (P < 0.05). The response to PGE2 was of a quadratic nature (P < 0.05) in which the lowest and the highest doses of PGE2 were associated with a greater production of progesterone than were the intermediate doses. Treatment of luteal cells with PGF2 alpha + LH or PGE2 + LH caused overall inhibition (P < 0.05) of progesterone production compared with treatment with each hormone alone. This interaction was not affected by the dose of LH used. These findings indicate that PGF2 alpha and PGE2 are involved in the autocrine control of corpus luteum function.     

Prostaglandins, not cyclic GMP, inhibit oxytocinase isoenzymes from human amniotic fluid in vitro

Two isoenzymes of oxytocinase (EC 3.4.11.3) activity were fractionated from human amniotic fluid samples between the 14th and 22nd weeks of gestation by Ultrogel acrylamide-agarose gel filtration and partially characterized. The isoenzymes were competitively inhibited by PGE1, PGE2 and PGF2 alpha more at pH 6.2 than at pH 6.8, whereas cyclic GMP (cGMP) and its 8-bromo derivative had no effect at either pH. The implications of these findings are discussed and it is suggested that since the activity of amniotic fluid oxytocinases is very low or minimal at or near term, inhibition of these by prostaglandins may not have physiological significance in the initiation of human parturition.     

Effect of prostaglandins on cyclic nucleotide levels in cultured keratinocytes.

Ginea pig ear epidermal cells (keratinocytes) were established in primary cultures using trypsin, and treated in their proliferative phase of growth with prostaglandins E1, D1, F1 alpha, E2, D2, or F2 alpha. This phase is induced by the addition of retinoic acid during cell plating. Intracellular content of cAMP and cGMP was measured by radioimmunoassay at various times after treatment. Maximum stimulation of cAMP levels was observed with PGD2, smaller increases with PGE2 and relatively transient rises with PGF2 alpha which were of low significance, but confirm earlier data. Similar results were observed with PGD1, PGE1, and PGF1 alpha with smaller increases. The effects of D and E PGs were biphasic. Significant increases in cGMP were immediately observed with PGD2 and PGE2. With PGF2 alpha, maximum cGMP levels were noted after some delay. All PGs tested showed some effect in elevating cyclic nucleotides in keratinocytes. The most striking result was the increase in cAMP on PGD2 treatment.     

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.     

Two Possibly Distinct Prostaglandin E1 Receptors in N1E-115 Clone: One Mediating Inositol Trisphosphate Formation, Cyclic GMP Formation, and Intracellular Calcium Mobilization and the Other Mediating Cyclic AMP Formation

Prostaglandin E1 (PGE1)-mediated transmembrane signal control systems were investigated in intact murine neuroblastoma cells (clone N1E-115). PGE1 increased intracellular levels of total inositol phosphates (IP), cyclic GMP, cyclic AMP, and calcium ([Ca2+]i). PGE1 transiently increased inositol 1,4,5-trisphosphate formation, peaking at 20 s. There was more than a 10-fold difference between the ED50 for PGE1 at cyclic AMP formation (70 nM) and its ED50 values at IP accumulation (1 microM), cyclic GMP formation (2 microM), and [Ca2+]i increase (5 microM). PGE1-mediated IP accumulation, cyclic GMP formation, and [Ca2+]i increase depended on both the concentration of PGE1 and extracellular calcium ions. PGE1 had more potent intrinsic activity in cyclic AMP formation, IP accumulation, and cyclic GMP formation than did PGE2, PGF2 alpha, or PGD2. A protein kinase C activator, 4 beta-phorbol 12 beta-myristate 13 alpha-acetate, had opposite effects on PGE1-mediated IP release and cyclic GMP formation (inhibitory) and cyclic AMP formation (stimulatory). These data suggest that there may be subtypes of the PGE1 receptor in this clone: a high-affinity receptor mediating cyclic AMP formation, and a low-affinity receptor mediating IP accumulation, cyclic GMP formation, and intracellular calcium mobilization.     

Rat osteogenic sarcoma cells:effects of some prostaglandins, their metabolites and analogues on cyclic AMP production.

Cyclic AMP production by freshly isolated cells, from a 32P-induced transplantable rat osteogenic sarcoma, was stimulated by PGE1, PGE2 and to a less extent by PGF2alpha and PGA2. In the case of PGE2, the cyclic AMP content of cells was maximal within 5 min. The 13,14-dihydroderivatives of PGE1, PGE2 and PGF2alpha had approximately 40% of the activity of the parent prostaglandin whilst, in every case, the metabolites (15-keto and 13,14-dihydro-15-keto) had very little activity. Two prostaglandin endoperoxide analogues (U44069 and U46619) had only 10% of the activity of an equimolar dose of PGE2. The data presented in this paper demonstrates similarities between the responses of these cells and cells derived from bony tissue in terms of the ability of prostaglandins to stimulate bone resorption in tissue culture.     

Interrelationship between nitric oxide and prostaglandins in bovine granulosa cells

It is well recognized that prostaglandins of the E (PGE) and F (PGF) series play an important role in ovarian physiology; in addition, nitric oxide (NO) has been recently demonstrated to be an important mediator of granulosa cell function. There is now evidence for a biologic relationship between PGs and the NO biosynthetic pathway. The aim of this study was to investigate the relationship between NO and PGE2 and PGF2alpha in bovine granulosa cells. Granulosa cells collected from small (<5mm) and large (>8mm) follicles were treated with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) or with indomethacin, an inhibitor of PGs synthesis, and PGE2 and PGF2alpha were quantified; in addition, the effects of PGE2 PGF2alpha and indomethacin on steroidogenesis and NO production were determined. The highest concentration of SNAP inhibited (P < 0.001) PGE2 production in cells from both kinds of follicles, while the lowest dose was effective only in cells from small follicles. The highest concentration of SNAP inhibited and stimulated (P < 0.001) PGF2alpha production in cells from small and large follicles, respectively. Progesterone (P4) production was stimulated by PGE2 and inhibited by PGF2alpha (P < 0.001) in cells from both types of follicles. Estradiol 17beta (E2) secretion was inhibited in cells from small and stimulated in those from large follicles by PGE2 (P < 0.05), while PGF2alpha was stimulatory in cells from both kinds of follicles (P < 0.001). P4 production by cells from small follicles was inhibited and stimulated by those from large follicles by indomethacin (P < 0.001), which also increased E2 output in cells from small follicles (P < 0.001). NO production was inhibited by both PGE2 and PGF2alpha except at the lowest concentration, which was stimulatory (P < 0.001). Indomethacin stimulated (P < 0.001) NO production. Taken together, the present data suggest a cross-talk between NO and PGs biosynthetic pathways, which needs to be further clarified.     

Prostaglandin E2 and F2 alpha inhibit growth of human gastric carcinoma cell line KATO III with simultaneous stimulation of cyclic AMP production

The effects of prostaglandins (PGs) on the growth of human gastric carcinoma cell line KATO III were investigated. PGE2 as well as PGF2 alpha significantly and dose-dependently inhibited the growth of this gastric carcinoma cell line (PGE2 greater than PGF2 alpha). This inhibition of cell growth by the PGs was associated with the increase in cyclic AMP production (PGE2 greater than PGF2 alpha), whereas inositol-phospholipid turnover was not affected by either PGE2 or PGF2 alpha as assessed by the formation of 3H-inositol phosphates. Furthermore, the proliferation of these gastric carcinoma cells was also suppressed by the administration of forskolin as well as of dibutyryl cyclic AMP. These results suggest that PGE2 and PGF2 alpha inhibit the growth of cultured human gastric carcinoma cells KATO III via stimulation of cyclic AMP production.     

Effects of dopaminergic drugs on the concentrations of PGE2 and PGF2alpha in various brain regions

It has long been shown by Biggio and Guidotti that multisynaptic nigro-cerebellar pathway of dopaminergic origin can control cerebellar cyclic guanosinmonophosphate (cGMP) content, a good index of the activity of Purkinje cells. In this line, it has been reported that haloperidol and sulpiride, significantly decrease cerebellar cGMP content while opposite changes are observed with apomorphine. In an attempt to establish whether other cerebellar cGMP-related parameters may be influenced by dopamine drugs. Authors have investigated the effects of haloperidol, sulpiride and apomorphine on cerebellar PGE2 and PGF2alpha. Results obtained indicate that haloperidol and sulpiride significantly reduce cerebellar PGE2 and PGF2alpha content while opposite changes are induced by apomorphine. Similar results have been observed in substantia nigra but not in other brain regions, such as corpus striatum and medial basal hypothalamus. The possibility that the observed changes in cerebellar PG-content may result from the modulation of striatal dopamine receptors is discussed.     

The effects of synthetic prostaglandin analogs on canine hepatic bile flow.

The synthetic prostaglandin analogs 16, 16-dimethyl PGF2 alpha and 16, 16-dimethyl PGE2 were administered to dogs with chronic biliary and gastric fistulas. The effects of 16, 16 diMePGF2 alpha and 16, 16 diMePGE2 were evaluated on bile flow and composition and bile adenosine 3', 5' monophosphate (cyclic AMP) secretion. 16, 16 diMePGF2 alpha in doses of 0.125 and 0.25 microgram-kg-min significantly increased hepatic bile flow. The choleresis was characterized by increased chloride and bicarbonate secretion. Measurement by radioimmunoassay of bile cyclic AMP concentration demonstrated no evident increase in bile cyclic AMP secretion associated with the choleresis produced by 16, 16 diMePGF2 alpha. The administration of 16, 16 diMePGE2 in a dose range 0.01 to 1.0 microgram-kg-min did not significantly alter bile flow rates or composition. Bile erythritol-14C clearance, a measure of canalicular bile flow, was significantly increased by PGF2 alpha but not by 16, 16-dimethyl PGF2 alpha, suggesting that the mechanism of action of PGF2 alpha in stimulating hepatic bile flow may be different from that involved in 16, 16-dimethyl PGF2 alpha choleresis. The results of this study indicate that the synthetic PGF2 alpha analog produces a choleretic response not mediated by adenylate cyclase and associated with increased chloride and bicarbonate secretion.     

Observations on prostaglandins in normal and leukemic human lymphocytes

Prostaglandins E (PGE) and F2 alpha (PGF2 alpha) were measured in lymphocytes of normal subjects, children with acute lymphocytic leukemia (ALL), and adults with chronic lymphocytic leukemia (CLL). In ALL lymphocytes PGE increased from a normal value of 25 pgrams to 270 pgrams/10(6) cells, and PGF 2 alpha increased from a normal value of 31 pgrams to 482 pgrams/10(6) cells. In CLL lymphocytes, levels of PGE and PGF2 alpha were normal or low. When normal lymphocytes were stimulated with phytohemagglutinin (PHA), the level of PGE and PGF2 alpha fluctuated, followed by corresponding changes in the level of cyclic nucleotides. In cultured ALL lymphocytes, the level of PGE remained high, while cyclic 3':5'-adenosine monophosphate (c-AMP) level was constantly low, and the initial level of PGF2 alpha fluctuated in relation to similar oscillations of cyclic 3':5'-guanosine monophosphate (c-GMP). These values were lower, although not significantly, when ALL lymphocytes were stimulated with PHA. When CLL lymphocytes were stimulated with PHA, the level of PGE remained low (20 pgrams), as did that of c-AMP. The level of PGF2 alpha, after a brief initial increase (130 pgrams), returned to and remained at a lower level (60 pgrams) while the level of c-GMP was persistently high. These results suggest: (1) prostaglandins may indirectly influence the cell cycle, possibly through modulation of cyclase activity and levels of cyclic nucleotides; and (2) some derangement of this regulatory mechanism may be present in leukemic lymphocytes.     

Structural specificity for prostaglandin effects on hepatocyte glycogenolysis.

Prostaglandins (PGs) are known to have effects on hepatic glucose metabolism. Some actions of PGs in intact liver systems may not involve PG effects directly at the level of the hepatocyte. To define the ability of structurally distinct prostaglandins to affect hepatocyte metabolism directly, the regulation of glycogenolysis was studied in hepatocytes isolated from male Sprague-Dawley rats. PGF and PGB2 inhibited glucagon-stimulated glycogenolysis in the hepatocyte system. Pinane thromboxane A2 (PTA2) and PGD2 had no effect on glucagon-stimulated glycogenolysis. Consistent with their inhibition of glucagon-stimulated glycogenolysis, PGF2 and PGF2 alpha inhibited glucagon-stimulated hepatocyte cyclic AMP accumulation. These actions of PGB2 and PGF2 alpha are identical with those previously reported for PGE2. Additionally, PGE2, PGF2 alpha and PGB2 inhibited glucagon-stimulated adenylate cyclase activity in purified hepatic plasma membranes. In contrast, PGF2 alpha, PGD2 and PTA2 were all without affect on basal rates of hepatocyte glycogenolysis or hepatocyte cyclic AMP content. PGE2 also inhibited glycogenolysis stimulated by the alpha-adrenergic agonist phenylephrine. Exogenous arachidonic acid was not able to reproduce the affects of PGE2 or PGF2 alpha on hepatocyte glycogenolysis, consistent with an extra-hepatocyte source of the prostaglandins in the intact liver. Thus PGE2 and PGF2 alpha act specifically to inhibit glucagon-stimulated adenylate cyclase activity. No prostaglandin tested was found to stimulate glycogenolysis. PGE2 and PGF2 alpha may represent intra-hepatic modulators of hepatocyte glucose metabolism.     

Placental lactogen as a regulator of luteal cells function during pregnancy in sheep

The luteotropic activity of ovine placental lactogen (oPL) on different days of gestation in ewes was assessed using in vitro methods. Corpora lutea (CL) harvested on Days 45, 70, 95, 120 and 135 of gestation and during parturition were enzymatically dispersed and plated on multiwell plates. After 48 h of incubation, all cultures were terminated and media were frozen for further steroid analysis. Cells were cultured in control medium, with addition of oPL alone, or in combination with PGE2 or PGF2alpha. Supplementation of culture media with oPL increased basal progesterone secretion by cells isolated on Days 45 and 70 of gestation. There was no effect on progesterone secretion by cells isolated on other days of gestation; PGE2 added to the culture media increased progesterone production only by cells isolated on Day 70 of pregnancy. Simultaneous oPL treatment with PGE2 had a statistically significant and stimulatory effect on progesterone production by luteal cells collected on Days 70 and 95 of pregnancy. In contrast, PGF2alpha alone in culture media decreased progesterone secretion by cells isolated on Days 45, 70 and 95 of gestation, while oPL plus PGF2alpha on Days 70 and 95 of gestation protected against luteolytic action of PGF2alpha. The results showed 1) a direct effect of the oPL on luteal cells isolated on Days 45 and 70 of gestation; 2) synergism between PL and PGE2 in progesterone production; by cells isolated on Day 70; 3) and a luteoprotective effect of oPL against the luteolytic action of prostaglandin F (PGF2alpha) observed on Days 70 and 95 of gestation.     

Distribution of cyclic nucleotides in layers of the cerebellum after decapitation

The distribution of the cyclic nucleotides was examined in layers of the mouse cerebellum following decapitation. Cyclic AMP increased and cyclic GMP decreased in all three layers of the cerebellum examined. The increase in cyclic AMP in the granular layer was far greater than in either the molecular or white layers. In the cerebellum from control mice, the cyclic GMP concentration was highest in the molecular layer and lowest in the white layer. Even after decapitation, this cyclic GMP gradient in the cerebellum was maintained.     

Prostaglandin biosynthesis and stimulation of cyclic AMP in primary monolayer cultures of epithelial cells from mouse mammary gland.

Cyclic AMP levels in primary monolayer cultures of epithelial cells prepared from mid-pregnant mice are stimulated by prostaglandin E1 and E2. Prostaglandin F1alpha and F2alpha have only a slight effect upon cyclic AMP levels. In the absence of phosphodiesterase inhibitors the rise in cyclic AMP produced by PGE1 is only transient and the levels return to normal within 30 minutes. High concentrations (16 mM) of theophylline are needed to prevent this decline, suggesting that the phosphodiesterase activity of epithelial cells in culture is high. However, theophylline alone produced only a small increase in basal cyclic AMP levels even over a 2-hour period indicating that basal cyclic AMP is turned over more slowly than cyclic AMP produced in response to stimulation with PGE1. Both PGE and PGF synthesis were monitored using radioimmunoassay procedures previously reported. The observed levels were found to decrease as cell density increased and were sensitive to the addition of agents such as collagen and naproxen.     

Modulation of normal and abnormal myeloid progenitor proliferation by cyclic nucleotides and PGE1

The effects of cyclic nucleotides and PGE1 upon the proliferation of normal granulocyte/macrophage progenitors were examined in in vitro systems and contrasted to the effects of these compounds on (1) granulocyte/macrophage progenitors from the peripheral blood of patients with myeolofibrosis/myeloid metaplasia (MF) and chronic myelogeneous leukemia (CML); and (2) blast progenitors from the peripheral blood of patients with acute myelogenous leukemia (AML) and acute monocytic leukemia (AMoL). Cyclic AMP was found to be a concentration dependent inhibitor of colony proliferation in all systems tested. Cyclic GMP was an inconsistent enhancer of colony proliferation in all systems in a manner which was not clearly concentration dependent. The effect of PGE1 in normal systems was highly variable depending on the culture conditions, but it was generally found to be an inhibitor of colony proliferation. Cyclic AMP, cyclic GMP and PGE1 altered the release of colony stimulating activity from adherent bone marrow cells in a manner opposite to the direct effects of these compounds on progenitor cell proliferation. Abnormalities in response to PGE1 were found in progenitors from patients with CML (deficient inhibition), AMoL (stimulation of proliferation in certain concentration ranges), and MF (enhanced proliferation). Studies on one of the patients with MF indicated that a normally responding population could be defined by density-gradient separation. These data confirm the capacity of these compounds to modulate in vitro proliferation of myeloid progenitors, and suggest that aberrations of response to PGE1 may occur in subpopulations of cells from several myeloproliferative disorders.     

Fetal and postnatal development of cyclic GMP phosphodiesterase activity in the rat brain

Cyclic GMP concentration and cyclic GMP phosphodiesterase activity were studied in rat mothers and fetuses at 17, 19 and 21 days of intrauterine life and 0, 1, 4, 10, 15,20, 30 and 45 days after birth. During this developmental period, the increase in cyclic GMP concentration was discrete and the value in 15-day-old rats was already similar to the adult level. Cyclic GMP phosphodiesterase activity increased from 17- to 19-day fetuses and was significantly reduced in 21-day fetuses, neonates, and 1-day-old rats. This reduction may be a result of fetal endocrine preparation for parturition. During postnatal development, cyclic GMP phosphodiesterase activity increased in a parallel way in the limbic system, corpora striata, cerebral hemispheres, and diencephalon, reaching maximal level between 20 and 30 days after birth, and then decreasing to the adult value. The highest activity was found in corpora striata and the lowest in diencephalon. Cerebellar cyclic GMP phosphodiesterase activity was very high in the 4-day-old rat (257% of adult value) and diminished significantly in the 10-day-old rat with no subsequent changes. Kinetic analysis of the enzyme during postnatal forebrain development showed an increase in both the V_max and the apparent K_m. A decrease in the enzyme's V_max was observed only in the cerebellum.The importance of cyclic GMP phosphodiesterase regulation of cyclic GMP concentrations in the brain during development is discussed.     

Prostaglandin E and E2 alpha secretion by glandular and stromal cells of the pig endometrium in vitro: effects of estradiol-17 beta, progesterone, and day of pregnancy.

Prostaglandins (PGs) are believed to play important roles in the establishment of pregnancy. Glandular and stromal cells were isolated from pig endometrium on days 11 through 19 of pregnancy and cultured in the presence of estradiol-17 beta (E2) and progesterone (P4) to determine the effect of day of pregnancy and steroids on the secretion of PGE and PGF2 alpha. Estradiol at concentrations between .01 and 1 microM did not affect PGE and PGF2 alpha secretion into the medium by glandular and stromal cells. Progesterone (.1 microM) suppressed (P less than .001) PGE and PGF2 alpha production from both cell types. Glandular cells secreted more (P less than .01) PGF2 alpha than PGE, whereas stromal cells collected on days 11, 12, 13, and 19 secreted more (P less than .05) PGE than PGF2 alpha. Stromal cells isolated from tissues collected on day 13 of pregnancy produced PGs with higher (P less than .01) PGE:PGF2 alpha ratio than those from tissues harvested on other days of pregnancy. Glandular cells isolated from tissues collected on days 13 and 19 and stromal cells isolated from tissue collected on day 13 of pregnancy secreted more (P less than .05) PGE and PGF2 alpha than cells isolated on other days of pregnancy. We conclude that: 1) P4 has a suppressing effect on PG secretion; 2) endometrial glandular and stromal cells each produce a unique profile of PGs; and 3) endometrial cells harvested on different days of pregnancy secrete different amounts of PGE and PGF2 alpha.     

Circadian variations in plasma 3':5'-cyclic adenosine monophosphate and 3':5'-cyclic guanosine monophosphate of normal adults.

Circadian variations in plasma cyclic AMP and cyclic GMP were studied in thirteen male subjects (20–22 years old) under controlled invironmental condition. Plasma collections were made every six hours. Cyclic AMP and cyclic GMP were determined by radioimmunoassay. Individual values of plasma cyclic AMP at 0800 are between 13.0 and 25.8 pmole/ml, and cyclic GMP between 2.5 and 7.0 pmole/ml. Cyclic AMP demonstrated the circadian variation with the maximum level at 1400 and the minimum at 0200, and cyclic GMP with the highest level at 1400 and the lowest level at 0800.