Prostacyclin Levels Research Articles

Plasma and Saliva Levels of PGI2 and TXA2 in the Headache‐Free Period of Classical Migraine Patients. The Effects of Nicardipine

The levels of Prostacyclin (PGI2) and Thromboxane A2 (TXA2) were assayed simultaneously (RIA) in the plasma and saliva of 9 patients suffering from classical migraine attacks. The assays were done during an attack-free period. In relation to the control group we observed a significant decrease in the plasma levels of PGI2 together with a sharp increase in TXA2 in saliva. When the patients were treated with nicardipine, a calcium antagonist, the TXA2 increase in saliva did not occur. These results suggest both a systemic and local effect in the classical migraine attacks. We explain and discuss our results by referring to the PGI2: TXA2 equilibrium system. Nicardipine action might be related to its ability to reduce the calcium entry into the cell induced by thromboxane.

Low level of prostacyclin as a risk of ischaemic heart disease

We have studied the relationship between levels of lipids and prostacyclin in 3- to 14-year-old children with a family history of ischaemic heart disease. The total levels of cholesterol in the serum of these children increased, while levels of the HDL-fraction and prostacyclin (measured as 6-keto-prostaglandin F 1a) decreased significantly. Levels of thromboxane B 2 in the plasma were unchanged. It is suggested that, in childhood, abnormalities of lipid metabolism co-exist with decreased levels of prostacyclin. The latter may be a new important indicator of early atherosclerotic disease.

Excessive secretion of vasopressin during vasovagal reaction

Vasovagal syncope elicits one of the most powerful transient vasodilatory responses in humans. Many studies have shown an altered neurohumoral response to tilting in patients with vasovagal syncope. Vasopressin (VP) has been of particular interest, but its exact role remains unclarified, whereas the possible role of the potent vasoactive end products of arachidonic acid metabolism has not yet been addressed. We determined the changes in plasma levels of VP, thromboxane (TXA2), and prostacyclin (PGI2) in 34 syncopal patients undergoing a standardized head-up tilt-table testing protocol and compared these changes between patients with positive and negative test results. Blood samples were collected at baseline, 15 minutes in the head-up position, and at the termination of the tilt test (the induction of syncope or the completion of a negative test). Sixteen patients had a positive test result, whereas 18 completed the test without developing any syncopal symptoms. In the tilt-positive group, VP levels presented a 20-fold increase at the time of syncope when compared with baseline levels (p = 0.0000), without any increase at earlier stages. No change was detected at any stage in the tilt-negative patients. We did not find any difference in the levels of PGI2 at any stage in any group of patients or between the 2 groups. TXA2 levels increased significantly at 15 minutes in the upright position in both tilt-positive and tilt-negative patients. No further increase was noticed at the time of syncope in the tilt-positive group, whereas in patients with a negative test result, there was a tendency to decline at the time of the test’s completion. It is concluded that although VP is markedly increased during tilt-induced vasovagal syncope, vasoactive amines such as TXA2 and PGI2 play a minor role in the vasodilatory component of the response.

Effect of high-dose methylprednisolone and U74006F on eicosanoid synthesis after subarachnoid hemorrhage in rats.

Free radicals and lipid peroxidation of membrane fatty acids are thought to play a role in the pathogenesis of arterial vasospasm and the physiopathologic patterns of neuronal damage after subarachnoid hemorrhage. We have evaluated the effects of treatment with either high-dose methylprednisolone every 8 hours or a single dose of U74006F on the temporal profile of ex vivo synthesis of four selected eicosanoids in brain slices after experimental induction of subarachnoid hemorrhage in rats. Prostaglandins D2 and E2, prostacyclin and leukotriene C4 levels were determined by radioimmunoassay after 1-hour incubation of the brain slices. The synthesis of prostaglandin D2 and 6-ketoprostaglandin F1 alpha at 48 hours after subarachnoid hemorrhage was significantly higher when compared to sham-operated animals (p = 0.01); prostaglandin E2 release was significantly enhanced at 6 hours after subarachnoid hemorrhage (p = 0.01). The release of the lipoxygenase metabolite was significantly enhanced at 1, 6, and 48 hours after subarachnoid hemorrhage induction. Both treatment regimens significantly reduced the ex vivo synthesis of prostaglandin D2, prostaglandin E2, and leukotriene C4 at 1, 6, and 48 hours after subarachnoid hemorrhage, whereas the effects on 6-ketoprostaglandin F1 alpha synthesis differed in the two treatment groups. U74006F enhanced the synthesis of prostacyclin metabolite in the early phase after subarachnoid hemorrhage, and high-dose methylprednisolone reduced the increasing synthesis at 48 hours. A strict comparison between the two treatments was not possible because of the different modalities of administration. However, these data suggest that the antioxidant effect of single-dose treatment with U74006F influenced the early and delayed effects on enzymatic lipid peroxidation, whereas the effects of methylprednisolone administration every 8 hours were more significant in the delayed phase.

Stimulatory Effects of Bradykinin on the Ovulatory Process in the in Vitro-Perfused Rat Ovary1

The role of bradykinin in the ovulatory process was investigated using an in vitro-perfused rat ovary model. Stimulation with LH (0.1 micrograms/ml) resulted in 2.6 +/- 0.5 (mean +/- SEM) ovulations per ovary, whereas no ovulations occurred in the nonstimulated control group. Bradykinin (5 microM) added to the perfusion system hourly for 10 h induced 2 of 5 ovaries to ovulate, with 2 and 3 ovulations, respectively. When bradykinin (5 microM) was given as a single dose at 5 or 10 h after LH, the ovulation rate was significantly increased to 11.0 +/- 2.8 and 8.6 +/- 2.0 ovulations per ovary, respectively. A competitive bradykinin antagonist, phenylalanine bradykinin, inhibited the bradykinin-induced increase in LH-stimulated ovulations. The addition of LH, but not of bradykinin, increased the levels of prostaglandin endoperoxide synthase in granulosa cells, but the levels of the enzyme in the residual ovarian tissue were negligible. In contrast, prostacyclin synthase was predominantly located in the residual ovarian tissue. This enzyme was not affected by LH or bradykinin. LH increased the tissue levels of prostaglandins, predominantly prostaglandin E2 (PGE2), at 7 h, whereas the stimulatory effect of bradykinin was smaller, with a preferential increase in prostacyclin (prostaglandin I2) levels. This study indicates a modulatory role of bradykinin, possibly involving prostacyclin late in the ovulatory process, in the rat.

Prostaglandin F1α levels during and after neonatal extracorporeal membrane oxygenation

Infants receiving extracorporeal membrane oxygenation therapy undergo long-term cardiopulmonary bypass, are systemically heparinized, and frequently receive platelet transfusions. Prostacyclin is a powerful inhibitor of platelet aggregation as well as a potent vasodilator. The levels of its stable metabolite prostaglandin F1 alpha increase significantly in children undergoing cardiopulmonary bypass during heart operations but decrease to preoperative levels after bypass. To determine the effect of long-term bypass on prostacyclin levels, multiple plasma samples were analyzed in 10 human neonates both during extracorporeal membrane oxygenation therapy and within 24 hours after extracorporeal membrane oxygenation. Prostaglandin F1 alpha, the stable metabolite of prostacyclin, was quantitated by radioimmunoassay in picograms per milliliter. Prostaglandin F1 alpha levels were elevated while the patients received extracorporeal membrane oxygenation therapy but decreased with duration of extracorporeal membrane oxygenation. In most infants, prostaglandin F1 alpha levels rose again during weaning from extracorporeal membrane oxygenation and remained elevated for 24 hours after extracorporeal membrane oxygenation. Extracorporeal membrane oxygenation course influenced circulating prostaglandin F1 alpha levels. Fluctuating prostaglandin F1 alpha levels are of clinical significance in the management of vasomotor tone and platelet function, common problems in the care and the prevention of hemorrhage in these critically ill infants.

Indomethacin attenuation of hepatic perfusion and plasma 6-ketoPGF1α elevations following glutathione depletion in rabbits

Glutathione (GSH) is important in detoxification and regulating cyclooxygenase activity. Since the liver has high levels of GSH, xenobiotic-induced changes in hepatic GSH could affect hepatic tissue blood perfusion (HP) via alterations in prostaglandin synthesis. In anesthetized male New Zealand rabbits, elevating GSH with GSH monoethyl ester had no affect on HP. Treatment of rabbits with diethyl maleate to deplete GSH also had no affect on HP in animals previously given GSH monoethyl ester. However, HP increased within 20 min in rabbits treated with diethyl maleate prior to GSH monoethyl ester. In another experiment, a similar rise in HP following GSH depletion was accompanied by arterial plasma 6-ketoPGF1α (the stable metabolite of prostacyclin) levels that were 4-times higher than in the controls. Plasma TxB2 (the stable metabolite of throm☐ane) also increased following diethyl maleate, but only to levels that were 25-times lower than for 6-ketoPGF1α. Since indomethacin blocked the rise in HP, as well as the increases in 6-ketoPGF1α and TxB2, these results indicate changes in HP may occur following GSH depletion as a result of increased synthesis of one or more arachidonic acid metabolites and implicate prostacyclin as a possible mediator of this phenomenon.

Effect of Antioxidant Therapy on Cyclooxygenase-Derived Eicosanoid Release during Intestinal Ischemia-Reperfusion

Conflicting data have been reported on the relationship between reactive oxygen intermediates and the formation of oxygenase-derived eicosanoids. Plasma levels of prostacyclin (PGI2, measured as the stable metabolite 6-keto-PGF1 alpha) and thromboxane A2 (TxA2, measured as TxB2) in the effluent blood of a canine ileal segment were determined following 1 or 2 h of ischemia. The synthesis of both eicosanoids was significantly stimulated during reperfusion, but extension of the ischemic interval from 60 to 120 min was not followed by a further increase. The role of oxidants potentially involved in the process was investigated by using materials that inactivate the xanthine-oxidase-generated intermediates. Previous studies on the same in vivo animal model had demonstrated the effectiveness of antioxidant therapy in reducing the postischemic histamine release. There was no significant alteration in the amount of eicosanoids synthesized following oral allopurinol, catalase, dimethylsulfoxide, mannitol or desferrioxamine treatment. Intravenously administered allopurinol, however, significantly elevated the postischemic 6-keto-PGF1 alpha/TxB2 ratio. The results suggest that these antioxidants at doses inhibitory to histamine liberation are not effective in influencing the postischemic eicosanoid release. Intravenously administered allopurinol could exert a potentially beneficial effect through a mechanism other than the blockade of xanthine oxidase.

Randomized trial of a selective inhibitor of thromboxane A2 synthetase, (E)-7-phenyl-7-(3-pyridyl)-6-heptenoic acid (CV-4151), for prevention of restenosis after coronary angioplasty.

A selective inhibitor of thromboxane A2 synthetase, CV-4151, has the unique property of increasing prostacyclin synthesis in addition to its anti-platelet aggregating effect. Prostacyclin inhibits the growth of smooth muscle cells which is considered to be an underlying mechanism of restenosis occurring after successful coronary angioplasty. A prospective randomized trial was conducted to determine whether CV-4151 could prevent restenosis. Administration was begun greater than or equal to 2 days before angioplasty, and continued until the follow-up study performed between 3 and 6 months after angioplasty. Follow-up angiography was performed in 58 patients (81 segments) taking the active drug and in 27 patients (35 segments) taking the placebo. The incidence of angiographic restenosis was 38.3% in the former group and 31.4% in the latter group. Thus, CV-4151 did not significantly reduce the incidence of restenosis, perhaps due to endothelial denudation after angioplasty preventing an increase of the subendothelial local prostacyclin level.

The antinociceptive activity of paracetamol in zymosan‐induced peritonitis in mice: the role of prostacyclin and reactive oxygen species

1. Oral administration of high doses of paracetamol (600 mg kg-1 or more) resulted in inhibition of the writhing and reduced the levels of prostacyclin (PGI2, measured as 6-keto-PGF1 alpha) induced by intraperitoneal administration of zymosan in mice. The high oral doses of paracetamol required were accompanied by behavioural toxicity which may have contributed to the inhibition of writhing. 2. The number of writhes per mouse and the proportion of mice writhing at least once correlated significantly with the levels of 6-keto-PGF1 alpha. However, inhibition of writhing by paracetamol occurred at higher levels of 6-keto-PGF1 alpha than was previously observed with acidic non-steroidal anti-inflammatory agents. 3. When injected i.p., PGI2, carbacyclin and iloprost (agonists at the PGI2 receptor) induced writhing. Intraperitoneal injection of PGI2 reversed the inhibition of writhing induced by indomethacin (1 mg kg-1, p.o.) but not that induced by oral administration of paracetamol. 4. Paracetamol at 800 mg kg-1, p.o., inhibited carbacyclin-induced writhing but indomethacin at 1 mg kg-1 p.o. did not. Paracetamol administered i.p. at 100 mg kg-1 reduced the peritoneal levels of 6-keto-PGF1 alpha and inhibited zymosan-induced but not carbacyclin-induced writhing and did not produce behavioural toxicity. 5. The in vitro potency of paracetamol as a prostaglandin synthesis inhibitor is known to be reduced by the presence of lipid peroxides. However, no lipid peroxides, measured as thiobarbituric acid reactive material, were detected in the peritoneal lavage fluid of zymosan-injected mice. 6. Intraperitoneal administration of a mixture of superoxide dismutase and catalase reduced detectable superoxide anion by 98% without inhibiting the writhing response to zymosan or the antinociceptive potency of paracetamol. 7. The data are consistent with the suggestion that inhibition of PGI2 synthesis in the peritoneal cavity by paracetamol is responsible for only a part of its antinociceptive activity in this test. However, extremely high oral doses of paracetamol were required which produced behavioural toxicity which clearly contributed to the inhibition of writhing. The low potency of paracetamol in this model cannot be attributed to the generation of lipid peroxides via the oxidative burst.

Mechanism of phosgene-induced lung toxicity: role of arachidonate mediators

We have previously shown that phosgene markedly increases lung weight gain and pulmonary vascular permeability in rabbits. The current experiments were designed to determine whether cyclooxygenase- and lipoxygenase-derived mediators contribute to the phosgene induced lung injury. We exposed rabbits to phosgene (1,500 ppm/min), killed the animals 30 min later, and then perfused the lungs with a saline buffer for 90 min. Phosgene markedly increased lung weight gain, did not appear to increase the synthesis of cyclooxygenase metabolites, but increased 10-fold the synthesis of lipoxygenase products. Pre- or posttreatment with indomethacin decreased thromboxane and prostacyclin levels without affecting leukotriene synthesis and partially reduced the lung weight gain caused by phosgene. Methylprednisolone pretreatment completely blocked the increase in leukotriene synthesis and lung weight gain. Posttreatment with 5,8,11,14-eicosatetraynoic acid (ETYA), a nonmetabolized competitive inhibitor of arachidonic acid metabolism, or the leukotriene receptor blockers, FPL 55712 and LY 171883, also dramatically reduced the lung weight gain caused by phosgene. These results suggest that lipoxygenase products contribute to the phosgene-induced lung damage. Because phosgene exposure did not increase cyclooxygenase synthesis or pulmonary arterial pressure, we tested whether phosgene affects the lung's ability to generate or to react to thromboxane. Infusing arachidonic acid increased thromboxane synthesis to the same extent in phosgene-exposed lungs as in control lungs; however, phosgene exposure significantly reduced pulmonary vascular reactivity to thromboxane but not to angiotension II and KCl.

Prostacyclin and prostaglandin E2 mediate reduction of increased mean arterial pressure during cardiopulmonary bypass by aspiration of shed pulmonary venous blood

Increased mean arterial pressure during the aortic crossclamp period while on cardiopulmonary bypass was usually treated by us with hypotensive drugs. We noticed, however, that aspirating shed excess pulmonary venous blood from the open pleural cavities causes an immediate reduction in mean arterial pressure, obviating the need for any further pharmaceutical intervention. In this study we investigated the relationship between the reduction in mean arterial pressure and the levels of prostacyclin and prostaglandin E2 in the peripheral and pulmonary venous blood. Ten men undergoing coronary bypass operations had 21 episodes of increased mean arterial pressure (106.9 +/- 11.4 mm Hg) during aortic crossclamping, which was reduced to 67.4 +/- 11.4 mm Hg (p less than 0.001) only by aspirating a mean of 490 ml (range 150 to 1100 ml) of pulmonary venous blood from the pleurae back into the circulation. Mean peripheral prostacyclin level, measured as 6-keto-prostaglandin F1 alpha, and prostaglandin E2 level, both measured by radioimmunoassay technique, were significantly lower at peak mean arterial pressure (419 +/- 180 and 59.5 +/- 21.2 pg/ml) than at lowest mean arterial pressure (632 +/- 271 and 96.7 +/- 52.4 pg/ml for 6-keto-prostaglandin F1 alpha and prostaglandin E2, respectively; p less than 0.001). Prostaglandin F1 alpha and prostaglandin E2 levels in the aspirated pulmonary venous blood were 2309 +/- 3098 pg/ml and 749 +/- 909 pg/ml, respectively. The hypotensive effect of shed pulmonary venous blood that is aspirated back from the pleurae into the circulation seems to be mediated by the high levels of prostacyclin and prostaglandin E2, both powerful vasodilators.

Roles of thromboxane and its inhibitor anisodamine in burn shock

Thromboxane (TXA 2) and prostacyclin (PGI 2) levels, circulatory platelet aggregate ratios (CPAR), CPK, LDH, GOT, platelet counts, blood viscosity, cortisol and urine epinephrine contents were determined in 42 burned patients who were divided into two groups: Group I control ( n = 34) and Group II ( n = 8) treated with TXA 2 synthesis inhibitor, anisodamine. It was found that in controls, both TXA 2 and the TXA 2/PGI 2 ratio increased significantly. There was no marked difference in PGI 2 levels between the two groups. Platelet counts and CPAR decreased, while blood viscosity, CPK, LDH, GOT, cortisol and epinephrine in the controls were all significantly higher than those found in Group II patients. All these findings suggested that the changes of TXA 2 and the TXA 2/PGI 2 ratios played an important role in the haemodynamics and haemorrheology in burn shock. The TXA 2 synthesis inhibitor, anisodamine, showed beneficial effects by restoring the haemodynamic and rheological disturbances towards normal by virtue of their ability to induce vascular constriction, platelet aggregation, cellular destruction, destabilization of membranes and release of chemical mediators (including enzymes). Furthermore, at 1–3 days postburn, the levels of CPK, LDH and GOT in controls were higher than those measured at 12 h postburn, but this phenomenon was not marked in the treated group, suggesting that after resuscitation, reperfusion damage had occurred and TXA 2 might be responsible for the damage. It is assumed that anisodamine could protect tissues from reperfusion damage. The findings also suggested that anisodamine could quicken the restoration of neuroendocrine disturbance initiated by shock (stress).

NMDA antagonists attenuate baroreflex in the rostral ventrolateral medulla of rats

A large scale screening test of the vasorelaxing actions of the extracts from Chinese herbs has been performed and the active principles were isolated: osthole from Angelica pubescens, protopine from Corydalis tubers, norathyriol from Gentianaceae, denudatin B and fargesone B from Magnolia fargesii, apigenin from Apium graveolens, and magnolol from Magnolia officinales. In this experiment, we tried to study the effects of these Chinese herbal principles on the vasoconstriction of rat thoracic aorta induced by high potassium solution, norepinephrine (NE) and caffeine, and to elucidate their modes of action. All the seven principles suppressed the contraction of rat thoracic aortic rings caused by cumulative concentrations of calcium (0.03-3 mM) in high potassium (60 mM) medium. They also relaxed the NE (3/tM)-induced contraction, and their pretreatment inhibited both the phasic and tonic contractions elicited by NE in the absence or presence of calcium (1.9 raN) in the medium. Indomethacin (20 pM) did not have any antagonizing effect on these relaxations. Osthole and magnolol also inhibited caffeine (I0 mM)-induced phasic contraction, while others did not have any effect. In quin-2-1oaded cultured rat vascular smooth muscle cells, NE-induced rises of intracellular calcium were suppressed by denudatin B and fargesone B. '~SCa++ uptakes induced by either NE or high potassium were inhibited by the seven vasorelaxants in a concentration-dependent manner. All these vasorelaxants did not change the levels of prostacyclin or cAMP of rat aorta. Both osthole and magnolol caused formation of cGMP in aorta, while other vasorelaxants did not have any effect or were effective only at higher concentrations than those relaxing the mu~!eo The cGMP increase and initial relaxation caused by magnolol were disappeared after the aorta was denuded. This endothelium-dependent relaxation by magnolol was antagonized by methylene blue (50/~M) and hemoglobin (10/~M) which were known to inhibit activation of guanylate cyclase and inactivate endothelium-derived relaxing factor (EDRF), respectively. in conclusion, seven vasorelaxants isolated from Chinese herbs inhibited vascular muscle contraction of rat aorta by suppressing the calcium i~flux through both voltage-gated and receptor-operated calcium channels. EDRE release by magnolol and cGMP increase by osthole may enhance their relaxing effects in rat aorta.

Plasma Levels of Fibronectin and Prostacyclin Metabolite in Peripartum Preeclamptic Women

Plasma fibronectin and prostacyclin levels have been reported to vary in preeclamptic women when compared with pregnant control women. Elevation of fibronectin and deficiency of prostacyclin have been postulated to be due to endothelial cell disruption or dysfunction. Eighteen preeclamptic women and 19 normal pregnant controls were evaluated for plasma levels of fibronectin and the prostacyclin metabolite 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha). 6-keto-PGF1 alpha and fibronectin plasma levels in patients were significantly different from control patients, with preeclamptic patients exceeding control subjects. Five patients had serial samples of 6-keto-PGF1 alpha prior to, during, and after intravenous magnesium sulfate therapy and no consistent effect was noted. No correlation existed between fibronectin and 6-keto-PGF1 alpha levels or between either compound and platelet count or liver function tests. Despite an overall elevation of fibronectin in preeclamptic patients, two patients with the hemolysis, elevated liver tests, and low platelet count syndrome showed low normal fibronectin levels coinciding with thrombocytopenia, hemolysis, and liver dysfunction. The magnitude of fibronectin elevation may therefore not predict the severity of preeclampsia. The significance of these findings is discussed.

Impaired prostaglandin E1/I2 receptor activity of human blood platelets in acute ischemic heart disease.

The platelets from 74 patients with acute myocardial infarction or with unstable angina showed decreased prostaglandin E1/I2 receptor activity when compared with that of 56 normal volunteers by using [3H]prostaglandin E1 as a probe. In normals, Scatchard analyses showed the presence of one high-affinity-low-capacity (Kd1 = 9.0 +/- 1.2 nM [mean +/- SD]; n1 = 120 +/- 30 sites/cell) and one low-affinity-high-capacity (Kd2 = 1.1 +/- 0.5 microM; n2 = 1,460 +/- 250 sites/cell) prostaglandin E1/I2 receptor population in platelets. In contrast (p less than 0.01), platelets from patients showed decreased ligand binding (n1 = 40 +/- 20 sites/cell; n2 = 800 +/- 210 sites/cell) with little change in the affinity of the receptors (Kd1 = 7.50 +/- 1.6 nM; Kd2 = 0.68 +/- 0.24 microM). On the other hand, the platelets from the patients with dilated cardiomyopathy (n = 7) who were hospitalized for acute chest pain but had normal coronary arteries did not show any impairment of the receptor activity. The plasma prostacyclin level of the patients with acute ischemic heart disease was similar to that of normal volunteers; this finding indicated that the defective receptor function was not related to the prostaglandin receptors occupancy in vivo. The impaired receptor activity was temporary in nature. The follow-up studies showed that the prostaglandin receptor activity of the patients' platelets improved to "normal" levels within 2-8 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Pro-inflammatory mediators induce sustained release of prostaglandin E2 from human dermal microvascular endothelial cells

The vasodilator prostaglandin E2 has been proposed as a mediator of erythema in a variety of cutaneous inflammatory reactions and prostacyclin levels have been found to be elevated in ultraviolet induced erythema. Human recombinant interleukin 1 alpha and lipopolysaccharide induced a concentration- and time-dependent release of prostaglandin E2, but not prostacyclin, from cultured neonatal and adult human dermal microvascular endothelial cells. Prostaglandin E2 was measurable at 2 h after stimulation with 1 U/ml interleukin 1 alpha, levels increased rapidly up to 6 h and more slowly up to 24 h. Lipopolysaccharide (20 micrograms/ml) induced measurable release of prostaglandin E2 between 2 and 4 h after stimulation and release continued up to 24 h when incubation was terminated. With both agonists, release of prostaglandin E2 was inhibited by indomethacin and significantly reduced by cycloheximide. The sensitivity and magnitude of responses of the cutaneous endothelial cells to these pro-inflammatory stimuli appeared to be dependent on their derivation.

Dose responses in platelet fatty acid composition, aggregation and prostanoid metabolism during moderate freshwater fish diet

The dose responses in platelet fatty acid composition, aggregation and thromboxane production and in plasma prostacyclin level during moderate freshwater fish diet was studied in healthy male students (n=100). There were four fish diet groups eating 0.9, 1.5, 2.3 or 3.8 fish-containing meals per week for 12 weeks. The meals provided about 0.25, 0.5, 0.6 or 1.1 g n-3 fatty acids per day, respectively. The increase of n-3 at the expense of n-6 fatty acids in total platelet lipids took place already with 1.5 weekly fish meals (0.5 g n-3 fatty acids/d). Most of the observed changes in platelet fatty acids were seen already after 5 weeks. ADP-and collagen-induced platelet aggregation was measured from controls and 1.5 and 3.8 fish meals per week groups. The maximum platelet aggregation values of the group with the highest fish intake were significantly lower than in the controls at the end of dietary period. A tendency towards reduced platelet aggregability was observed also in the group eating 1.5 fish meals per weeks. Thromboxane B 2 and 6-keto-PGF 1α were determined from controls and two groups with highest fish intake. The highest intake was needed to decrease the thromboxane B 2 production of clotted blood and the plasma 6-keto-PGF 1α concentration. A positive correlation between ADP-induced aggregation and thromboxane B 2 production was found. These results show that platelet characteristics can already be modified with a very moderate freshwater fish intake.

Platelet Aggregation in Flowing Blood at a Site of Injury to an Endothelial Cell Monolayer: Quantitation and Real-Time Imaging with the TAB Monoclonal Antibody

Epifluorescence videomicroscopy permits real-time imaging of platelet adhesion/aggregation to a defined microinjury of a monolayer of endothelial cells exposed to flowing blood. The fluorescent label is the TAB murine monoclonal antibody directed against human platelet GP IIB, together with a fluorescein-conjugated goat F(ab')2 against murine immunoglobulin. The combination assures specificity for platelet membranes, yet leaves platelet function intact. TAB is first added to gently mixed, citrated human blood; the second antibody is added 1 hour after the first, mixing continuing for a second hour. Bovine aortic endothelial cell monolayers (ECMs), grown on rectangular cover glasses precoated with microfibrillar collagen, comprise one wall of a flow chamber mounted on a vertical microscope stage. A loop of 6-0 sterile suture is drawn across the ECM in order to create microinjuries of width 70 +/- 15 microns (mean +/- SD) oriented in a direction transverse to flow. Platelet adhesion/aggregation is virtually absent on intact and confluent regions of the monolayer. On micro-injury sites and at shear rates of 60 to 1,080 sec-1, however, computer-enhanced images obtained by means of videomicroscopy show arrival and adherence of single platelets resulting in the formation of platelet aggregates elongated in the flow direction. When the monolayers are pretreated with 1.0 mmol/L lysine acetylsalicylate, the mean aggregate thickness increases (2P less than .05) to 260 +/- 58% (mean +/- SE, N = 6) of control, aggregates are regularly shed downstream, and the surface area of the injury site covered by platelets is augmented (2P less than .05) from 14.8 +/- 3.9% to 49.2 +/- 4.7% (mean +/- SE, N = 6). Donor ingestion of aspirin, on the other hand, leads to an increase (2P less than .01) in percent surface coverage to 42.7 +/- 8.5 without a concomitant increase in mean aggregate thickness. In parallel with the above, outflow levels of serum thromboxane and prostacyclin are measured by radioimmunoassays (RIAs) for thromboxane B2 and 6-Keto-PGF1 alpha, respectively. Thromboxane B2 is increased (2P less than .01) by monolayer pretreatment with lysine acetylsalicylate from 5.08 +/- 1.47 to 9.35 +/- 2.42, but decreased (2P less than .05) after oral aspirin to 1.21 +/- 0.38 ng/mL (mean +/- SE, N = 6). Levels of 6-Keto-PGF1 alpha were reduced (2P less than .05) by monolayer pretreatment from 0.48 +/- 0.046 to 0.36 +/- 0.016 ng/mL. Platelet adhesion/aggregation at a site of injury to an endothelial cell monolayer, therefore, can be imaged in flowing blood in real time using a monoclonal antibody approach.(ABSTRACT TRUNCATED AT 400 WORDS)

Platelet aggregation in flowing blood at a site of injury to an endothelial cell monolayer: quantitation and real-time imaging with the TAB monoclonal antibody

Epifluorescence videomicroscopy permits real-time imaging of platelet adhesion/aggregation to a defined microinjury of a monolayer of endothelial cells exposed to flowing blood. The fluorescent label is the TAB murine monoclonal antibody directed against human platelet GP IIB, together with a fluorescein-conjugated goat F(ab')2 against murine immunoglobulin. The combination assures specificity for platelet membranes, yet leaves platelet function intact. TAB is first added to gently mixed, citrated human blood; the second antibody is added 1 hour after the first, mixing continuing for a second hour. Bovine aortic endothelial cell monolayers (ECMs), grown on rectangular cover glasses precoated with microfibrillar collagen, comprise one wall of a flow chamber mounted on a vertical microscope stage. A loop of 6–0 sterile suture is drawn across the ECM in order to create microinjuries of width 70 +/- 15 microns (mean +/- SD) oriented in a direction transverse to flow. Platelet adhesion/aggregation is virtually absent on intact and confluent regions of the monolayer. On micro-injury sites and at shear rates of 60 to 1,080 sec-1, however, computer-enhanced images obtained by means of videomicroscopy show arrival and adherence of single platelets resulting in the formation of platelet aggregates elongated in the flow direction. When the monolayers are pretreated with 1.0 mmol/L lysine acetylsalicylate, the mean aggregate thickness increases (2P less than .05) to 260 +/- 58% (mean +/- SE, N = 6) of control, aggregates are regularly shed downstream, and the surface area of the injury site covered by platelets is augmented (2P less than .05) from 14.8 +/- 3.9% to 49.2 +/- 4.7% (mean +/- SE, N = 6). Donor ingestion of aspirin, on the other hand, leads to an increase (2P less than .01) in percent surface coverage to 42.7 +/- 8.5 without a concomitant increase in mean aggregate thickness. In parallel with the above, outflow levels of serum thromboxane and prostacyclin are measured by radioimmunoassays (RIAs) for thromboxane B2 and 6-Keto-PGF1 alpha, respectively. Thromboxane B2 is increased (2P less than .01) by monolayer pretreatment with lysine acetylsalicylate from 5.08 +/- 1.47 to 9.35 +/- 2.42, but decreased (2P less than .05) after oral aspirin to 1.21 +/- 0.38 ng/mL (mean +/- SE, N = 6). Levels of 6-Keto-PGF1 alpha were reduced (2P less than .05) by monolayer pretreatment from 0.48 +/- 0.046 to 0.36 +/- 0.016 ng/mL. Platelet adhesion/aggregation at a site of injury to an endothelial cell monolayer, therefore, can be imaged in flowing blood in real time using a monoclonal antibody approach.(ABSTRACT TRUNCATED AT 400 WORDS)