Plasma Prostanoid Research Articles

THROMBOXANES: THE LINK BETWEEN INTRALIPIDS AND PULMONARY VASOCONSTRICTION IN THE NEWBORN

During intralipid (IL) infusion, premature neonates demonstrate significant decreases in p0 which are accompanied by pulmonary vasoconstriction. The mechanism by which intralipids induce these changes is not yet known. This study was undertaken to evaluate the hypothesis that IL, via the provision of increased fatty acid precursors, acts by Increasing biosynthesis of the vasoconstricting prostanoid, thromboxane.Thirteen neonates (<1750 grams) who had not yet been fed, and were not expected to receive any enteral nutrition for 5 days were randomized to receive either TPN with IL (n=7) or TPN without IL (n=6). Plasma prostanoid levels were drawn on day 1, 3 and 5 of study and results are as follows:The data are consistent with the following conclusions: 1. IL provide increased essential fatty acid prostaglandin precursors; 2. These increased EFA precursors result in increased biosynthesis of the vasoconstricting prostanoid, thromboxane; and 3. Thromboxane thus produced may contribute to the observed pulmonary vasoconstriction.

Effects of kallidinogenase on urinary kallikrein excretion and plasma prostanoid concentrations in patients with essential hypertension.

The effects of kallidinogenase on urinary kallikrein excretion, plasma immunoreactive prostanoids and platelet aggregation were investigated in patients with essential hypertension. Urinary kallikrein excretion and plasma 6-keto PGF1 alpha concentration were significantly decreased in these patients. Significant decreases in blood pressure, as well as significant increases of urinary kallikrein excretion and plasma 6-keto PGF1 alpha concentration after kallidinogenase administration were also observed.

Topical ibuprofen decreases thromboxane release from the endotoxin-stimulated burn wound.

A full-thickness burn wound in adult sheep releases prostanoids when they are injected locally with E. coli endotoxin, 2 micrograms/kg, resulting in an increase in pulmonary artery pressure (Ppa) from 20 +/- 3 to 34 +/- 5 mm Hg, and a decrease in mean arterial oxygen tension (PaO2) from 88 +/- 6 to 70 +/- 5 torr; this corresponds to an increase in venous plasma TxB2 content from a baseline of 220 +/- 79 pg/ml to 440 +/- 90 pg/ml. Burn prostanoid production, measured in lymph, increased ten- to fifteen-fold for both thromboxane A2, measured as TxB2, and prostacyclin, 6-keto-PGF1 alpha. The intravenous administration of ibuprofen, 12.5 mg/kg, eliminated both the increase in Ppa and decrease in PaO2 as well as the increase in burn lymph prostanoids. However, plasma prostanoids were also decreased below baseline, a potentially deleterious effect. A topical ibuprofen cream, 5% ibuprofen in a water-soluble ester, was applied to the burn hide every 6 hrs x 4 after which endotoxin was again injected below the hide. The pulmonary dysfunction was prevented as was the increase in plasma TxB2 with the value remaining at baseline. Burn lymph levels were only increased three- to five fold. Ibuprofen levels in burn lymph were maintained at 1-2 mcg/ml. The addition of the cream to the burn, however, did increase the wound bacterial content to 10(5)-10(7) bacteria/gram of tissue compared to 10(2)-10(3) for the dry, untreated burn, probably due to softening of the burn. Topically applied ibuprofen, therefore, can decrease burn wound prostanoid production from local endotoxin, preventing lung dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative evaluation of particulate and soluble glucan in an endotoxin model

Particulate glucan (P) but not soluble glucan (F) has been shown to sensitize rats to endotoxins. This phenomenon is believed to be mediated by the reticuloendothelial system (RES). The effect of glucan-P and -F on the RES, and the response of glucan-treated rats to nonlethal doses of endotoxin were investigated. Rats were injected for 5 days with 10 mg/kg of glucan-P, -F or saline. Three days later rats were either (1) injected with colloidal carbon for clearance studies, (2) sacrificed for organ histology and determination of serum glucose, plasma thromboxane (Tx) B 2, and plasma 6-keto-prostaglandin (PG) F 1α concentrations, or (3) challenged with a nonlethal dose of endotoxin. The latter were further subdivided into groups for either 30-day survival or for sacrifice at 30 min or 4 h post-endotoxin infusion to obtain blood samples for glucose, TxB 2, and 6-keto-PGE 1α determinations. Glucan-P induced hepatosplenomegaly and granulomatous changes within the liver and spleen. The carbon clearance halftime was markedly decreased in these animals. In glucan-P-treated rats challenged with endotoxin, elevated concentrations of both plasma prostanoids were observed as well as alterations in serum glucose levels. These changes were less pronounced in glucan-F- or saline- treated rats. Following endotoxin challenge, only 40% of glucan-P-treated rats survived 30 days whereas 100% of both the glucan-F- and saline- treated rats survived. We conclude that glucan-P, in contrast to glucan-F, significantly heightens RES function and that this effect likely accounts for the endotoxin sensitivity.

Determination of peripheral plasma prostanoid concentration: an unreliable index of 'in vivo' prostanoid activity.

Plasma concentrations of PGE2, PGF2 alpha, 6-keto-PGF1 alpha and TxB2 were determined in 4 healthy volunteers by gas chromatography-negative ion chemical ionization mass spectrometry. TxB2 concentrations in all volunteers increased with time during blood collection, increases occurred more sporadically in the case of PGE2, PGF2 alpha and 6-keto-PGF1 alpha. Rapid changes in plasma prostanoid concentrations within a sampling series were unpredictable and were inexplicable. The measured plasma prostanoid concentrations apparently depended on the sampling conditions, which could not be adequately standardized and controlled. However, very short term changes in plasma prostanoid levels cannot be excluded.

Ibuprofen prevents Pasteurella hemolytica endotoxin-induced changes in plasma prostanoids and serotonin, and fever in sheep.

Intravenous infusion of Pasteurella hemolytica endotoxin caused marked increases in the plasma levels of thromboxane B2 (TxB2), prostaglandins (PG) and serotonin in sheep. The control values for TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and serotonin before endotoxin infusion averaged 283 +/- 53 (standard error of mean), 281 +/- 14 and 199 +/- 27 pg/ml and 57 +/- 3 ng/ml, respectively. At 50 min during endotoxin infusion, these values were increased to their maximum of 376, 339, 325 and 202% of control, respectively. Body temperature increased from the control value of 39.5 +/- 0.1 degrees C to a maximum of 41.5 +/- 0.1 degrees C at 200-300 min of infusion. In the second part of this study, we have examined the effects of ibuprofen on endotoxin-induced increases in plasma PG, TxB2, and serotonin levels and body temperature. The control values for TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and temperature prior to ibuprofen and endotoxin infusion averaged 238 +/- 35, 335 +/- 44 and 248 +/- 28 pg/ml, 65 +/- 3 ng/ml and 40.1 +/- 0.2 degrees C, respectively. A loading dose (15 mg/kg) of ibuprofen was followed by infusion of endotoxin (12 micrograms/kg) and ibuprofen (43.3 mg/kg) over 500 min. Plasma levels of 6-keto-PGF1 alpha and serotonin increased only to 131 and 149% of control at 50 min of infusion, and levels of PGF2 alpha and TxB2 decreased to 50 and 80% of control at 100 and 150 min of infusion, respectively. Temperature remained unchanged. Ibuprofen effectively suppressed endotoxin-induced increases in the plasma levels of TxB2, 6-keto-PGF1 alpha, PGF2 alpha, and serotonin and body temperature. It was concluded from the present study that nonsteroidal anti-inflammatory drugs as an adjunct to antibiotic therapy might have a rational basis in treatment of endotoxin toxicity.

Extracorporeal membrane oxygenation and congenital diaphragmatic hernia: Modification of the Pulmonary vasoactive profile

We studied the vasoactive profile of a term infant with congenital diaphragmatic hernia and intractable pulmonary hypertension who was refractory to conventional medical management despite an early stable period. Plasma prostanoid vasoconstrictor thromboxane A2 (TxB2) levels were elevated prior to ECMO at 150pg/mL, rose to 310pg/mL with the first hour of bypass and remained elevated until 72 hours by which time they fell to less than 50pg/mL. This coincided with the decreased extracorporeal circulatory support needed to maintain systemic arterial pO2 between 70 to 90 torr. Pulmonary vasodilator prostacyclin (6-keto-PGF1 alpha) was minimally elevated prior to bypass a 50pg/mL and became undetectable. Catecholamine levels were markedly elevated prior to ECMO at 4,000pg/mL with no demonstrable pulmonary extraction of norepinephrine. Though catecholamine levels remained nonspecifically elevated, pulmonary metabolism of norepinephrine improved with bypass time to 48% at 96 hours and coincided with the overall improvement of the infant's respiratory function. These data suggest pulmonary hypertension associated with congenital diaphragmatic hernia is at least partially precipitated by alterations in prostanoid homeostasis as selective activation of thromboxane synthetase pathways rather than nonspecific activation of the entire archidonate cascade. While ECMO per se may have no lasting effect on prostanoid homeostasis, ECMO can allow a period of cardiopulmonary rest during which more physiologic prostanoid levels are established. Although activation of the sympatho-adrenal axis may contribute to pulmonary hypertension, the role of catecholamines in this infant is not clear. Return of the lungs ability to clear norepinephrine may be an additional marker of biologic lung recovery.

Re-examination of the assay for plasma prostanoids by solid-phase extraction, and radioimmunoassay

A method for the routine assay of plasma thromboxane and prostacyclin metabolites, thromboxane B 2 and 6ketoprostaglandin F 1α (employing solid phase extraction to remove the metabolites from interfering substances) and using commercially available antisera for their radioimmunoassay has been investigated. Modifications of previously published procedures have been explored, including the use of non-explosive solvents in the extraction procedure, and inclusion of a non-cross reacting internal standard, prostaglandin D 2, to estimate recovery through the extraction procedures. Both the original and modified procedures can produce high blank values, which apparently result from the solid-phase extraction. These high backgrounds are constant for a given lot of solid phase extraction cartridges and can be corrected by subtraction. The modified method is linear with volume of plasma assayed to as little as one ml, and all cross-reacting material in normal human plasma was found to co-chromatograph with authentic standards on reverse-phase high performance liquid chromatography. Values for normal adult plasmas were found to be 0.44 ±.15 pmol/ml 6keto PGF i1α (mean ± SD) and .103±.07 for thromboxane B 2. The method reported provides a convenient, reproducible way to assay these important plasma prostanoids.

The role of thromboxane in primate endotoxin shock

Previous studies have suggested an important role of thromboxane (Tx) in the pathogenesis of endotoxin shock in the rat. The present study evaluated the role of thromboxane in an LD 70 primate model of endotoxin shock by administering 6 mg/kg of endotoxin to three groups of animals that were pretreated with either saline (5 ml), OKY 1581 (2 mg/kg, 10 min prior), or imidazole (25 mg/kg/hr starting 30 min prior), groups I, II, and III, respectively. There were significant differences between the groups with respect to changes in MAP, PAP, and CO. OKY 1581 effectively blocked endotoxin-induced increase in plasma Tx. However, as a result of shunting of the endoperoxides into the prostacyclin pathway, there was a greater increase in plasma 6-keto PGF 1α, the stable hydrolysis product of prostacyclin. Imidazole augmented the formation of both prostacyclin and Tx. Despite the differences in plasma prostanoids, there was no difference between the groups with respect to changes in platelet or WBC counts, nor in survival: I ( 4 10 ); II ( 4 10 ); III ( 2 6 ). Conclusions: (i) endotoxin-induced neutropenia and decrease in the platelet count are not Tx mediated; (ii) Tx is not solely responsible for the decrease in CO during endotoxin shock; (iii) it is possible to prevent endotoxin-induced increase in the PAP by either blocking Tx formation or by increasing endogenous PGI 2 production; and (iv) Tx may not be a major contributing factor in the mortality of endotoxin shock in baboons.

1640 PROSTACYCLIN DEFICIENCY DOES NOT PLAY A PIVOTAL ROLE IN HEMOLYTIC UREMIC SYNDROME (HUS)

A decrease in the prostacyclin (PGI2) stimulating activity of plasma has been reported in children with HUS. Although no study has attempted to assess plasma PGI2 levels themselves, the presence of a decrease in the PGI2 stimulating activity has been equated with a deficiency of PGI2 in HUS. We have conducted an evaluation of plasma prostanoids (PGI2 and TXB2) in 5 children admitted to SUNY during an epidemic of HUS in the northeast and in 23 controls. We were unable to document a pivotal role for PGI2 deficiency in HUS. Using an RIA for plasma 6KPGF1α(the stable hydrolysis product of PGI2), patients with HUS demonstrated elevated 6KPGF1α levels of 1.05±0.3 (1SD) pmol/ml when compared to controls (0.41±0.13; p<0.001). Increased production of PGI2 in HUS was accompanied by a concomitant increase in plasma thromboxane. Compared to a plasma TXB2 level of 0.10±0.06 in controls, the mean level in patients with HUS was 0.33±0.09pmol/ml (p<0.001). When the ratio of plasma TXB2 to 6KPGF1α was evaluated as an index of proaggregatory and vasoconstrictor versus antiaggregatory and vasodilator influences, no difference was observed between controls (0.33±0.06) and HUS (0.33±0.08). Changes in prostanoid production in HUS appear to reflect vascular injury (T6KPGF1α) and concomitant platelet consumption (↑TXB2). A deficiency of PGI2 in HUS was an attractive hypothesis that explained the systemic hypertension and the observed thrombocytopenia. Our finding however does not support a role for prostacyclin deficiency, and underscores the heterogenousness of HUS.

Relationships between the severity of myocardial ischaemia, reperfusion-induced ventricular fibrillation, and the late administration of dazmegrel or nifedipine.

We examined the effects of late administration of the thromboxane synthetase inhibitor dazmegrel (UK 38485) and the calcium channel blocker nifedipine in anaesthetised greyhounds subject to occlusion of the left anterior descending coronary artery with reperfusion after 40 min of ischaemia. Administration of dazmegrel, 3 mg/kg i.v., or nifedipine, 5 micrograms/kg + 1 microgram kg-1 min-1 i.v., 25 min after coronary artery occlusion failed to reduce the incidence of reperfusion-induced ventricular fibrillation (controls, 70%; dazmegrel, 50%; nifedipine, 70%; n = 10). Measurement of plasma prostanoid concentrations indicated that within 5 min of receiving dazmegrel there was a significant reduction in thromboxane B2 concentrations in the local coronary vein draining the ischaemic myocardium. The results suggest that the occurrence of reperfusion-induced ventricular fibrillation depends upon the severity of changes occurring during ischaemia. Analysis of various factors suggested that the number of ischaemia-induced arrhythmias, heart rate, and the magnitude of changes in local coronary venous PO2 may be important predictors of reperfusion-induced ventricular fibrillation.

Simultaneous determination of prostanoids in plasma by gas chromatograp—negative-ion chemical-ionization mass spectrometry

A method for simultaneous determination of prostaglandin E 2 (PGE 2), prostaglandin F 2α (PGF 2α), 6-keto-prostaglandin F 1α (6-keo-PGF 1α), and thromboxane B 2 (TxB 2) in plasma was developed. After acidification and addition of 2H- and 3H-labelled internal standards, plasma prostanoids were extracted by reversed-phase cartridges and purified by normal-phase high-performance liquid chromatography. The pentafluorobenzyl, methoxime, trimethylsilyl derivatives were formed. Negative-ion chemical-ionization mas spectra with methane as reagent gas show on intense peak at m/ z (M — pentafluorobenzyl). This ion was used for selective-ion monitoring. Prostanoid plasma concentrations (pg/ml) in five healty volunteers were: PGE 2 2.0–10.4, PGF 2α 2.2–9.8, 6-keto-PGF 1α 0.6–1.8, and TxB 2 3.0–45.3. However, there is evidence that the TxB 2 values may frequently be falsely high because of ex vivo production during the sampling procedure.

Plasma thromboxane B2, 6-keto PGF1 alpha and cyclic nucleotides levels as related to treadmill exercise test in patients with ischemic heart disease.

Plasma prostanoids and levels of cyclic nucleotides were studied in forty-nine outpatients with precordial pains and subjected to the treadmill exercise test. Blood samples were drawn before, immediately after and 30 minutes after exercise, from antecubital veins. Plasma TXB2, 6-keto PGF1 alpha, cyclic AMP and cyclic GMP levels were measured by radioimmunoassay. The results of exercise tests were evaluated according to the treadmill exercise score (TES) of Hollenberg et al. Patients were divided into two groups; those with TES (-) with ischemic findings in exercise and those with TES (+) with normal exercise response. There were no differences in TXB2 levels between the two groups before exercise. Immediately after exercise statistically significant differences in TXB2 levels were present between the two groups. There were increased levels in the TES (-) group and decreased levels in the TES (+) group (p less than 0.01). Although the 6-keto PGF1 alpha levels were the same between the two groups before exercise, 6-keto PGF1 alpha levels in the TES (+) group increased significantly immediately after exercise. Similar changes were noted in the case of cyclic nucleotides, and the differences increased immediately after exercise. We conclude that high responses of cyclic nucleotides and PGI2 are required to counteract increases in levels of TXA2 and diminution of these responses may be an important phenomenon involved in the physiological status of ischemic heart disease.

Development of quantitative analysis of plasma thromboxane B2 by gas chromatography-mass spectrometry.

In order to diagnose patients in thrombotic state, it is quite important to detect increased concentration of plasma thromboxane B2 (TXB2), a stable catabolite of TXA2. To determine plasma TXB2 levels with high sensitivity and selectivity, we employed gas chromatography-mass spectrometry (GC/MS). The trimethylsilyl (TMS) ether derivatives conventionally employed in GC/MS analysis of prostanoids are not suitable for quantitation of plasma prostanoids, because the mass spectra are deficient in ions with high intensity in the high mass range and TMS ether derivatives are sensitive to moisture. To solve these problems we employed tert-butyldimethylsilyl (t-BDMS) ether derivatives, based on the observation that t-BDMS ether derivatives afforded abundant ions at [M-57]+ and showed good hydrolytic stability. The reaction conditions of tert-butyldimethylsilylation were also examined to optimize the selected ion monitoring response. The t-BDMS ether derivatives of prostanoids were successfully analyzed with a short capillary column with a relatively large diameter, with maintaining good separation. In conjunction with the use of reversed-phase high performance liquid chromatography as purification procedure, a sensitive and reproducible stable isotope dilution assay of plasma TXB2 was developed. The values obtained by this method correlated well with those obtained by the radioimmunoassay we have developed.

Effects of anesthesia and surgery on prostanoid concentrations in plasma and pulmonary lymph

Comparisons were made of plasma and pulmonary lymph concentrations of 6-keto-PGF 1α and thromboxane B 2 between chronic and acute models of the sheep lung lymph fistula preparation. Pentobarbital anesthetized sheep subjected to acute thoracotomy and artificially ventilated demonstrated significantly elevated pulmonary lymph concentrations of 6-keto-PGF 1α and TxB 2 for two hours following surgery while venous or arterial plasma prostanoid concentrations increased to a much lesser degree over the same time period. No changes in plasma or lymph prostanoid concentrations were observed in the unanesthetized, chronic lung lymph preparation during a similar baseline observation period. The rates of decrease of pulmonary lymph prostanoid concentrations in the acute model following surgical preparation suggest the requirement of a three hour stabilization period after completion of all surgical procedures before pulmonary arachidonic acid metabolism reaches steady-state conditions.

心疾患とThromboxane(第III報)

Forty-nine outpatients with precordial pains were studied by the treadmill exercise test. Before, immediately after and 30 minutes after exercise, blood samples were obtained from antecubital veins, measuring plasma TXB2, 6-keto PGF1α, cyclic AMP and cyclic GMP levels by radioimmunoassay. The results of exercise tests were evaluated with the treadmill exercise score (TES) by Hollenberg et al, by which the patients were divided into two groups, TES (-) with ischemic findings in exercise and TES (+) with normal exercise. Changes of plasma prostanoids and cyclic nucleotides in each group were analyzed. There were no differences in TXB2 levels between two groups before exercise. Immediately after exercise statistically significant difference of TXB2 levels were present between two groups, resulting from the increased levels in TES (-) group and decreased in TES (+) group (p<0.01). Although 6-keto PGF1α levels also showed no differences between two groups before exercise, 6-keto PGF1α levels in TES (+) group were increased statistically significantly immediately after exercise. In consequence statistically significant differences (p<0.01) were observed between two groups and between the levels before exercise and immediately after exercise in TES (-) group. Similar changes were present in cyclic nucleotiedes, especially cAMP levels before exercise between two groups (p<0.05) and their differences increased more immediately after exercise (p<0.01). In ischemic heart disease, prostaglandins might play an important roles, especially the failure of PGI2 production to counteract to the increase of TXA2 by exercise may be an important phenomena to know the physiological conditions of ischemic heart disease.

Plasma prostanoids in pregnancy-induced hypertension.

The concentrations of 13,14-dihydro-15-oxo-prostaglandin F2 alpha (PGFM), 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha) and thromboxane B2 (T X B2) were measured by radioimmunoassay in peripheral plasma from 183 pregnancy women attending routine antenatal clinics. A total of 141 patients (47 nulliparous, 94 parous) remained normotensive and had uncomplicated pregnancies. The results from this group showed that there was no significant difference in the concentration of any metabolite in relation to parity or gestational age. The concentrations (pmol/l; means +/- SD) were PGFM 373 +/- 105, 6-oxo-PGF1 alpha 391 +/- 104 and T X B2 373 +/- 121. Nineteen patients (12 nulliparous, 7 parous) who had pregnancy-induced hypertension (PIH) by the time of sampling (three) or who subsequently developed the symptom (mean time from sampling to diagnosis 11 weeks, range 1-24 weeks) had significantly higher levels of 6-oxo-PGF1 alpha (574 +/- 216; P less than 0.0005, Student's t-test) and T X B2 (603 +/- 268; P less than 0.0005). The concentrations in seven nulliparous patients with PIH and proteinuria were 656 +/- 276 for 6-oxo-PGF1 alpha and 754 +/- 228 pmol/l for T X B2.

Effects of AZ-1355 on plasma prostanoid levels and lung metastasis of B-16 melanoma tumors

Effects of AZ-1355 on plasma prostanoid levels and lung metastasis of B-16 melanoma tumors

Phospholipase A2 stimulated release of prostanoids from the isolated, perfused rabbit liver: implications in regional cellular injury.

We have previously demonstrated a direct relationship between the activity of the arachidonic acid cascade in vivo and the extent of cellular damage following several types of experimental injury. Since phospholipase activity has been shown to regulate arachidonic acid availability, we tested the ability of circulating phospholipase A2 (PLA2) of pancreatic origin to stimulate prostanoid production or induce cellular injury in the isolated, perfused rabbit liver. Experimental conditions were similar to those present during pancreatitis or early splanchnic artery occlusion shock. The administration of PLA2 at a rate of 100 U/min for 10 min resulted in enhanced rates of thromboxane B2 and 6-ketoprostaglandin F1 alpha release between 1 and 5 min into the infusion period. No changes in hepatic perfusion pressure, vascular resistance, wet tissue weight, or release of lactic dehydrogenase or acid phosphatase into the effluent were observed in either vehicle or PLA2-treated livers. This indicates that cellular injury was not a factor in the prostanoid release. These data suggest that circulating PLA2 can directly stimulate de novo prostanoid synthesis in noninjured tissues. Thus, enhanced plasma prostanoid concentrations in intact animals during periods or regional cellular injury may be due in part to circulating PLA2 released from damaged tissues.