Plasma Thromboxane B2 Levels Research Articles

Antithrombin III activity, von Willebrand factor antigen and platelet function in young diabetic patients treated with multiple insulin injections versus insulin pump treatment

In a prospective study with cross-over design 20 patients with insulin-dependent diabetes mellitus of more than 2 years duration were treated for 6 months with continuous subcutaneous insulin infusion (CSII) and multiple insulin injections (MII). Metabolic control, platelet aggregability, thromboxane B2 levels in serum and plasma as well as antithrombin III (ATIII) activity and von Willebrand factor antigen were evaluated. A good metabolic control was obtained by both intensified regimens. No difference could be demonstrated between either platelet function tests or serum level of von Willebrand factor antigen during treatment with CSII and MII. However, the plasma level of ATIII activity was significantly higher (P less than 0.01) during MII treatment as compared to CSII treatment. There was no correlation between ATIII activity and daily insulin requirement or serum fructosamine. In conclusion, long-term metabolic control with MII has a favourable effect on ATIII activity in plasma. This may be important for a delay in onset and progression of diabetic vascular complications.

Lower torso ischemia-induced lung injury is leukocyte dependent.

Lower torso ischemia leads on reperfusion to sequestration of polymorphonuclear leukocytes (PMN) in the lungs and increased permeability. This study tests the role of circulating leukocytes (WBC) in mediating this lung injury. Anesthetized sheep prepared with chronic lung lymph fistulae underwent 2 hours of bilateral hind limb tourniquet ischemia. In untreated controls (n = 7), 1 minute after reperfusion there were transient increases in mean pulmonary arterial pressure (MPAP) from 13 to 38 mmHg (p less than 0.05) and pulmonary microvascular pressure (Pmv) from 7 to 18 mmHg (p less than 0.05), changes temporally related to a rise in plasma thromboxane (Tx) B2 levels from 211 to 735 pg/ml (p less than 0.05). Lung lymph TxB2 levels rose from 400 to 1005 pg/ml at 30 minutes (p less than 0.05), and remained elevated longer than plasma levels. Lung lymph flow (QL) rose from 4.3 to 8.3 ml/30 minutes (p less than 0.05) after 30 minutes of reperfusion and remained elevated for 2 hours. The lymph/plasma (L/P) protein ratio was unchanged from 0.6, while the lymph protein clearance increased from 2.6 to 4.6 ml/30 minutes (p less than 0.05), suggesting increased microvascular permeability. WBC counts decreased within the first hour of reperfusion from 6853 to 3796/mm3 (p less than 0.05), and lung histology after 2 hours showed proteinaceous exudates and leukosequestration of 62 PMN/10 high-powered fields (HPF), higher than the 22 PMN/10 HPF (p less than 0.05) in sham animals (n = 3). Recruitment of the pulmonary vasculature by left atrial balloon inflation (n = 3) resulted in a rise in MPAP to 20 mmHg. After 3 hours of balloon inflation, QL stabilized at 9.8 ml/15 minutes, and a pressure-independent L/P protein ratio of 0.3 was achieved. During reperfusion, QL increased further to 11.2 ml/15 minutes, the L/P ratio rose to 0.56 and the calculated osmotic reflection coefficient decreased from 0.70 to 0.44, documenting an increase in lung microvascular permeability. In contrast to these untreated ischemic controls, sheep (n = 7) rendered leukopenic with hydroxyurea or nitrogen mustard and having a total WBC count of 760/mm3 and PMN count of 150/mm3 did not manifest reperfusion-induced increases in MPAP, Pmv, QL, lymph protein clearance, or lung lymph. TxB2 level (p less than 0.05). Plasma TxB2 levels rose slightly at 30 minutes from 199 to 288 pg/ml (p less than 0.05). Lung histology was normal. These data indicate that WBC mediate the ischemia-induced increase in pulmonary microvascular permeability.

Limb ischemia-induced increase in permeability is mediated by leukocytes and leukotrienes.

This study tests the role of white blood cells (WBC) and leukotrienes in mediating the increased microvascular permeability following ischemia and reperfusion. Anesthetized dogs (n = 23) underwent 2 hours of hind limb ischemia induced by tourniquet inflation to 300 mmHg. In untreated animals (n = 7), tourniquet release led after 5 minutes to a rise in plasma thromboxane (Tx) B2 levels from 360 to 1702 pg/ml (p less than 0.05); after 2 hours, lymph TxB2 concentration had risen from 412 to 1598 pg/ml (p less than 0.05). There were decreases in circulating WBC from 11,766 to 6550/mm3 and platelets from 230 to 155 x 10(3)/mm3. During reperfusion, popliteal lymph flow (QL) increased from 0.07 to 0.24 ml/hour (p less than 0.05), while the lymph/plasma (L/P) protein ratio was unchanged from 0.39, changes consistent with increased microvascular permeability. WBC depletion (n = 7) to 302/mm3 by hydroxyurea or nitrogen mustard attentuated (p less than 0.05) the reperfusion induced rise in plasma TxB2 from 91 to 248 pg/ml and prevented the increase in lymph TxB2 concentration. Within 5 minutes of tourniquet release WBC counts further decreased to 191/mm3 (p less than 0.05) and platelets declined from 175 to 93 x 10(3)/mm3 (p less than 0.05). QL increased from 0.07 to 0.12 ml/hour (p less than 0.05), lower than untreated animals (p less than 0.05), and the L/P protein ratio declined from 0.49 to 0.37 (p less than 0.05), dilutional changes consistent with increased filtration pressure but not permeability to protein. Pretreatment with the lipoxygenase inhibitor diethylcarbamazine (DEC) (n = 8) prevented the reperfusion-induced increase in plasma and lymph TxB2 levels (p less than 0.05) and the fall in WBC counts (p less than 0.05), while platelet counts declined from 381 to 210 x 10(3)/mm3 (p less than 0.05). QL rose from 0.09 to 0.23 ml/hour (p less than 0.05) during reperfusion, and the L/P protein ratio of 0.3 remained unchanged, a value lower than in untreated dogs (p less than 0.05). In two animals of each group, vascular recruitment was induced by tourniquet inflation to 50 mmHg. This led to a high QL of 0.25 ml/hour and a low L/P ratio of 0.18. In untreated animals during reperfusion, QL further increased to 1.3 ml/hour, and L/P ratio rose to 0.44, documenting increased vascular permeability. In contrast, reperfusion in leukopenic or diethylcarbamazine (DEC)-treated dogs with vascular recruitment, was not associated with increases in QL or the L/P protein ratio.(ABSTRACT TRUNCATED AT 400 WORDS)

Erythrocyte morphologic features and serum chemistry studies in ovine pregnancy-induced hypertension treated with thromboxane synthetase inhibitors

Erythrocyte morphologic characteristics and serum chemistry results were studied in 10 gravid ewes during experimental ovine pregnancy-induced hypertension and subsequent administration of the thromboxane synthetase inhibitors CGS13080 and CGS12970. During the hypertensive period mean arterial blood pressure, plasma thromboxane B2 levels, and serum chemistry results, and electrolyte levels were significantly altered. Parameters returned to baseline values or were improved after drug administration. Erythrocyte morphologic features did not change significantly with the onset of the syndrome. Echinocytosis was present during baseline measurement and persisted throughout hypertension. However, after thromboxane synthetase inhibition, percentages of discocytes increased (p ≤ 0.005) with the same frequency that echinocyte numbers decreased (p ≤ 0.05). Schistocytes were present throughout the study, and changes in their numbers were not detected. Serum phosphorus, blood urea nitrogen, and bilirubin levels and anion gap rose significantly during hypertension and returned to normal levels after drug treatment. We speculate that CGS13080 or CGS12970, by decreasing thromboxane levels and blood pressure, promoted the normalization of erythrocyte membranes.

Inhibition of atherosclerosis by fish oil in cholesterol-fed rabbits

To evaluate the effects of dietary fish oil on cholesterol-induced atherosclerosis, 36 New Zealand rabbits in four groups were fed a 0.3% cholesterol diet for 10 weeks. One group served as control, whereas groups I, II and III received 1, 2 and 3 ml/day, respectively, of fish oil (Protochol, eicosapentaenoic acid, 180 mg, and docosahexaenoic acid [DHA], 120 mg/ml). The percent of aortic and pulmonary atherosclerosis was measured by planimetry of sudanophilic lesions. The percent of aortic lesions in the control group was 59 ± 22%. The two higher dose fish oil groups showed a significant reduction in aortic lesions: group I (40 ± 26%, p = NS), group II (18 ± 11%, p < 0.01) and group III (36 ± 22%, p < 0.05). Area of pulmonary artery lesions was significantly higher in the control group (48 ± 22%) as compared with group I (15 ± 13%, p < 0.01), group II (4 ± 3%, p < 0.01) and group III (8 ± 9%, p < 0.01).The high cholesterol diet in the control group decreased bleeding time from 82 ± 17 to 59 ± 22 s (p < 0.05). Groups II and III showed an increased bleeding time (62 ± 15 to 84 ± 17 s and 66 ± 22 to 95 ± 27 s; p < 0.05, respectively). Fish oil did not signifcantly alter total serum cholesterol and high density lipoprotein (HDL cholesterol. In group II triglyceride decreased from 128 ± 22 to 64 ± 25 mg/dl (p < 0.001). Plasma thromboxane B2levels decreased to the same extent in all four groups. There was no correlation between thromboxane B2levels and percent of aortic or pulmonary atherosclerosis. However, there was a modest correlation between percent lesions in the pulmonary artery and aorta (r = 0.6).This study shows that dietary fish oil can attenuate the development of aortic and pulmonary atherosclerosis in cholesterol-fed rabbits. The increased bleeding time appears to confirm the known antiplatelet effects of fish oil.

Effect of naloxone and ibuprofen on organ blood flow during endotoxic shock in pig.

The effects of an opiate antagonist naloxone and a cyclooxygenase inhibitor ibuprofen on organ blood flow during endotoxic shock were evaluated in a fluid-resuscitated porcine endotoxic shock model. Radiolabeled microspheres were used to measure regional blood flow. Escherichia coli endotoxin (0.1 mg/kg), infused intravenously over 40 min, reduced mean arterial blood pressure to 50 mmHg and systemic vascular resistance to 57% of control without affecting cardiac output. Endotoxin reduced blood flow to cerebrum (to 49% of control), kidney (to 25% of control), spleen, and skeletal muscle, while blood flow to left ventricle, stomach, and small and large intestines were unaffected. Sixty minutes after endotoxin administration, animals were randomized to one of three groups. Group I animals were controls and received no drug, group II animals received ibuprofen (12.5 mg/kg iv), and group III animals received naloxone (2 mg/kg iv) 60 min after endotoxin. Ibuprofen increased mean arterial blood pressure to 80 mmHg and increased blood flow to both cerebrum (to 92% of control) and kidney (to 47% of control). Plasma levels of thromboxane B2 and 6-ketoprostaglandin F1 alpha were increased 8- and 16-fold, respectively, after endotoxin, and both were decreased by ibuprofen. Naloxone increased mean arterial blood pressure to 62 mmHg but had no effect on regional blood flow or plasma cyclooxygenase metabolite levels. These data suggest that cyclooxygenase metabolites may contribute to decreased mean arterial blood pressure and reduced organ blood flow during endotoxic shock in the pig.

Platelet aggregation and thromboxane B2 release in patients with acute myocardial infarction--their relation to coronary patency.

Platelet function in the aortic blood in 39 patients who underwent intracoronary thrombolysis with urokinase was evaluated in the acute stage of myocardial infarction and after 4 weeks. The patients were classified into 2 groups according to the patency of the infarct vessel shown by coronary arteriography before urokinase administration. In the acute stage, 26 patients with completely occluded infarct vessel (group 1) showed a decreased level of platelet aggregation induced by adenosine diphosphate or arachidonic acid as compared with 13 patients with patent infarct vessel (group 2). The platelet aggregation in group 1 increased 4 weeks later and both groups showed similarly enhanced platelet aggregation levels as compared with normal controls. Like platelet aggregation, serum thromboxane B2 production in group 1 was lower than that in group 2 in the acute stage. Plasma thromboxane B2 levels in the aorta in both groups were significantly elevated in the acute stage, and were normalized after 4 weeks. This elevation of thromboxane B2 seems to be due to its washout from the infarct vessel, because plasma thromboxane B2 levels were significantly higher in the great cardiac vein than those in the aorta after successful reperfusion in group 1 or group 2. In conclusion, despite a significant elevation in plasma thromboxane B2 levels, platelet aggregation and serum thromboxane B2 production relatively decrease in patients with totally occluded infarct vessel. The patency of the infarct vessels should be taken into account when evaluating platelet function in acute myocardial infarction.

Effect of Thromboxane Synthetase lnhibition on Platelet Function and Morphology During Ovine Pregnancy-Induced Hypertension

Arterial blood pressure, serum fibrin/fibrinogen degratory products, plasma thromboxane B2, in vitro platelet aggregation, and platelet ultrastructure were studied in ten gravid ewes during fast-triggered ovine pregnancy-induced hypertension and subsequent administration of the thromboxane synthetase inhibitors CGS13080 and CGS12970. During the hypertensive period, blood pressure (p less than 0.005) and plasma thromboxane B2 levels (p less than 0.005) were significantly altered. Collagen-induced in vitro platelet aggregation lag times increased (p less than 0.01), and percent aggregation (p less than 0.05), primary (p less than 0.01), and secondary (p less than 0.005) aggregatory slopes decreased. Collagen also failed to induce aggregation in some ewes. Primary slopes of ADP-induced in vitro platelet aggregation decreased (p less than 0.01) during hypertension. Degranulation and open canalicular tubule system swelling were observed in platelets which produced abnormal or no aggregation response. However, these ultrastructural abnormalities did not necessarily correspond to hypertensive periods. Thromboxane synthetase inhibitor administration lowered blood pressure (p less than 0.005) and plasma thromboxane B2 levels (p less than 0.005). Abnormalities in collagen and ADP-induced platelet aggregation curves were also corrected, and ultrastructural abnormalities were not detected. Marked elevations in plasma thromboxane levels during ovine pregnancy-induced hypertension may have had an "exhaustive" effect on thrombocytes which was reversed by thromboxane synthetase inhibition.

Raised plasma thromboxane B2 levels in experimental acute necrotizing pancreatitis in rats. The effects of flunarizine, dazoxiben, and indomethacin.

The possible role of thromboxane A2 (TXA2) in acute necrotizing pancreatitis (ANP) was investigated in rats. After ANP was induced by injecting sodium taurocholate (5% w/v) into the pancreatic duct, the thromboxane B2 (TXB2) levels in plasma increased significantly. The effects of indomethacin, a general blocker of prostaglandin synthesis, on survival time and on plasma TXB2 levels were compared with those of dazoxiben, a more specific blocker of TXA2 synthesis, and Flunarizine, a calcium entry blocker known to inhibit the effects of TXA2. In a test group without any treatment, all animals died within 30 h of ANP induction. Although TXB2 levels were lowered by the administration of indomethacin, dazoxiben, and Flunarizine, survival times were not significantly altered. Indomethacin pretreatment had no beneficial effect, whereas 30% and 40% of the animals survived for 36 h after treatment with Flunarizine and dazoxiben, respectively. The results of the present study indicate that inhibition of TXA2 synthesis alone does not dramatically alter survival time. However, a potential role for other arachidonate metabolites in ANP cannot be ruled out by this study.

Effect of prostaglandin and leukotriene antagonists in acute mesenteric artery occlusion.

Superior mesenteric artery occlusion leads to mesenteric ischemia, activation of arachidonic acid metabolism and release of endotoxins into the systemic circulation. The effect of leukotriene and prostaglandin antagonists on hemodynamic response and survival of rats after superior mesenteric artery (SMA) occlusion was investigated. The animals were divided into five groups: in group 1 (n = 105) the SMA was clamped for 2 h and mortality assessed after 24 h. Group 2 animals (n = 20) were pretreated with 5 mg/kg indomethacin and the SMA clamped similarly to group 1, group 3 animals (n = 15) were pretreated with 5 mg/kg Voltaren, group 4 animals (n = 20) received 20 mg/kg BW 755C before mesenteric artery occlusion, and group 5 animals (n = 50) were pretreated with 100 mg diethylcarbamazine. The blood pressure and pulse response as well as histologic appearance of the bowel 1 h after declamping was similar in all five groups. The mortality rate after 24 h was 34% in the control group, 36% with indomethacin treatment, 36% with voltaren, 47% with BW 755C and 40% with diethylcarbamazine. The mortality rate in all the treated groups was not significantly different from the control group. Plasma thromboxane B2 levels were inhibited significantly by indomethacin and Voltaren and to a lesser extent by BW 755C. There was a paradoxical rise in thromboxane B2 following diethylcarbamazine treatment. It is concluded that inhibition of the cyclooxygenase and/or the lipoxygenase pathways of arachidonic acid did not alter the hemodynamic response and mortality following 2 h of acute superior mesenteric artery occlusion.

Mediators of C5a-induced bronchoconstriction.

Previous studies had suggested that histamine and products of arachidonate metabolism were mediators of the bronchoconstriction induced in guinea pigs by the complement cleavage product C5a. The present study was conducted to further define the arachidonate metabolite(s) involved. Tracheal airflow and transpulmonary pressure were measured in anesthetized and artificially ventilated guinea pigs and pulmonary resistance and dynamic lung compliance were calculated as a measure of bronchoconstriction. The effect of the peptido-leukotriene antagonist L-649,923 and the thromboxane synthetase inhibitor U-63557A on the C5a-induced bronchoconstriction was determined. Also, the response to C5a was evaluated in animals made tachyphylactic to the bronchoconstrictor actions of LTB4. C5a-induced bronchoconstriction was not altered in animals treated with L-649,923 or made tachyphylactic to LTB4 suggesting that LTB4 and peptido-leukotrienes are not major mediators of the response. C5a challenge caused a significant increase in plasma thromboxane B2 levels which was prevented in part by the thromboxane synthetase inhibitor U-63557A. In addition, C5a-induced bronchoconstriction was significantly inhibited by U-63557A. Thus, these studies suggest that thromboxane is the arachidonate metabolite at least in part responsible for C5a-induced bronchoconstriction.

Effects of chronic administration of doxorubicin on plasma levels of prostaglandins, thromboxane B2, and fatty acids in rats.

The effects of multiple doses of doxorubicin (DXR) on hematocrit and plasma levels of prostaglandins (PG), thromboxane B2 (TxB2), total lipid, esterified and free fatty acids, and proteins were investigated in male rats. The rats received DXR (2 mg/kg) or vehicle weekly by the subcutaneous route for 2, 4, 8, and 13 weeks and were killed 1 week after their last dose. Another group of rats treated for 13 weeks was sacrificed at 19 weeks, 6 weeks after the last dose. No changes in hematocrit or plasma PG, TxB2, or total levels of fatty acids were noted between control and DXR-treated rats at either 3, 5, or 9 weeks. The hematocrit was slightly depressed from control levels at 14 and 19 weeks. Plasma PGE, PGF2 alpha, and TxB2 were elevated over control levels at 14 and 19 weeks. Plasma 6-keto-PGF1 alpha was increased over the control level only at 19 weeks. Total plasma lipid and esterified fatty acids were highly elevated over control levels at 14 and 19 weeks. Plasma free arachidonic acid was elevated over control levels at 14 and 19 weeks, while levels of other free fatty acids were unchanged. Plasma protein levels were slightly depressed from control levels at 3, 9, and 14 weeks. Elevations of plasma free arachidonic acid, PG, TxB2, esterified fatty acids, and total lipid might be involved in cardiotoxicity and nephrotoxicity found with chronic administration of DXR.

Effects of a selective thromboxane synthetase inhibitor (OKY-046) in patients with coronary artery disease during exercise.

We studied the levels of thromboxane B2 (TXB2), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), platelet aggregability, beta-thromboglobulin and platelet factor 4 in 30 coronary artery disease (CAD) patients and 21 normal subjects during exercise. During treadmill exercise, 13 of 30 CAD patients reported chest pain. We administered a selective thromboxane synthetase inhibitor (OKY-046) for 2 weeks to 10 CAD patients with exercise-induced chest pain and studied its effects. At rest, the plasma TXB2 levels and platelet aggregation were significantly lower in normal subjects than in CAD patients, and there was no difference between CAD patients with and without exercise-induced chest pain. On treadmill testing, plasma TXB2 levels and platelet aggregation increased significantly only in the CAD patients with exercise-induced chest pain. Plasma 6-keto-PGF1 alpha levels in normal subjects were significantly higher than those in CAD patients both at rest and during exercise. After administration of OKY-046, mean exercise time increased significantly from 7.5 to 8.6 min (p less than 0.001). Plasma TXB2 level and platelet aggregation decreased significantly after OKY-046 administration both at rest and during exercise. These results suggest that a marked increase in TXA2, with only a minimal change in PGI2, during exercise may contribute to exercise-induced myocardial ischemia, and that OKY-046 is useful in the treatment of CAD patients.

Pulmonary and systemic consequences of localized acid aspiration: Manny J, Manny N, Lelcuk S, et al. Surg Gynecol Obstet 162:259, 1986

Acid aspiration may recruit a generalized inflammatory reaction that can potentiate the local injury. After surgical isolation of bronchi in a group of 15 dogs, 1 milliliter per kilogram of 0.37 normal hydrochloric acid was instilled into either side. After five minutes, platelet and white blood cell counts fell to 10,000 and 1,000 per cubic millimeter (p less than 0.05). Platelet aggregates were noted in blood smears. 111Indium-platelet activity doubled over both the aspirated and nonaspirated lung (p less than 0.05). Physiologic dead space rose from 18 to 67 per cent and to 46 per cent in the aspirated and nonaspirated lung (p less than 0.05). Physiologic shunt increased from 12 to 47 per cent and to 43 per cent (p less than 0.05) on the two sides. Plasma thromboxane B2 levels at 30 minutes rose from 0.28 to 0.93 nanograms per milliliter (p less than 0.05). Edema fluid from the aspirated lung had thromboxane B2 values of 2.87 nanograms per milliliter, indicating pulmonary synthesis. Within five minutes of aspiration, systemic effects were prominent; mean arterial pressure fell from 114 to 46 milliliters of mercury (p less than 0.05), and the cardiac index fell 24 per cent from 106 to 81 milliliters per kilogram per minute (p less than 0.05) along with an 18 per cent decrease in contractility of a rat papillary muscle bathed in plasma from the aspirated dog. Mean pulmonary arterial pressure rose from 12 to 18 millimeters of mercury (p less than 0.05). Despite fluid infusion at 36 milliliters per kilogram per hour to keep wedge pressure constant at 5.5 millimeters of mercury, and sampling of one-third the blood volume, hemoglobin concentration rose 0.9 grams per cent (p less than 0.05) indicating increased microvascular permeability. At autopsy, the aspirated and nonaspirated lung were indistinguishable with congestion, interstitial hemorrhage, and white blood cell infiltrates. Systemic organs showed vascular congestion and edema. These data demonstrate that local aspiration leads to generalized inflammatory sequelae with cardiopulmonary failure.

Prostaglandin metabolism in children with diabetes mellitus. I. Plasma prostaglandin E2, F2 alpha, TXB2, and serum fatty acid levels.

To study prostaglandin (PG) metabolism in children with insulin-dependent diabetes mellitus, plasma levels of PGE2, PGF2 alpha, and thromboxane B2 and the composition of serum fatty acids were measured. Platelet aggregation, a risk factor in diabetic vascular complications, was also measured. The mean levels of plasma PGE2 and PGF2 alpha were high and serum dihomo-gamma-linolenic acid and arachidonic acid were low in the diabetic children. The plasma thromboxane B2 levels of the diabetic children and normal controls were not significantly different. Platelet aggregation was also increased in diabetic patients. These results suggest that the insulin deficiency and high blood sugar in diabetic children may disturb the supply of dihomo-gamma-linolenic acid from cis-linoleic acid, decreasing prostaglandin formation in series 1. Then feedback regulation may increase production of PGE2 and PGF2 alpha in series 2. Altered PG metabolism may be responsible for the occurrence and progression of vascular complications in the diabetic children.

Prostaglandin Metabolism in Children With Diabetes Mellitus. I. Plasma Prostaglandin E2, F2α, TXB2, and Serum Fatty Acid Levels

SummaryTo study prostaglandin (PG) metabolism in children with insulin‐dependent diabetes mellitus, plasma levels of PGE2, PGF2α, and thromboxane B2 and the composition of serum fatty acids were measured. Platelet aggregation, a risk factor in diabetic vascular complications, was also measured. The mean levels of plasma PGE2 and PGF2α were high and serum dihomo‐gamma‐linolenic acid and arachidonic acid were low in the diabetic children. The plasma thromboxane B2 levels of the diabetic children and normal controls were not significantly different. Platelet aggregation was also increased in diabetic patients. These results suggest that the insulin deficiency and high blood sugar in diabetic children may disturb the supply of dihomo‐gamma‐linolenic acid from cis‐linoleic acid, decreasing prostaglandin formation in series 1. Then feedback regulation may increase production of PGE2 and PGF2α in series 2. Altered PG metabolism may be responsible for the occurrence and progression of vascular complications in the diabetic children.

Cigarette smoking and platelet function

To assess the influence of cigarette smoking on platelet activation, we studied the changes in intraplatelet and platelet-released serotonin (5-HT) and plasma levels and platelet-associated production of thromboxane B2 (TXB2), in 6 non smokers and 6 habitual smokers, before and after acute exposure to smoke. Before smoking, habitual smokers showed slightly higher, albeit not significantly, 5-HT platelet concentrations and TXB2 plasma levels, as well as lower TXB2 platelet production after collagen and even more after ADP stimulation (0.59±0.27 vs 1.35±0.46 and 0.99+0.47 vs 2.08±0.51 ng/108 platelets for habitual smokers vs controls, 4 and 10 min after ADP, p<0.02). No significant differences in platelet 5-HT release were observed. Acute smoking did not induce any significant change from baseline in either 5-HT or TXB2 for controls, while significantly reduced TXB2 production from ADP-challenged platelets from habitual smokers (0.30±0.15 vs 0.59±0.27 ng/108 platelets, immediately after smoking vs baseline, p<0.01). Ninety min after the completion of the smoking, the values had returned to baseline. Immediately after smoking, significant differences were found between habitual smokers and controls for TXB2 platelet production (2.76±1.78 vs 6.42±1.60, p<0.025 and 3.01±1.90 vs 6.44±2.26 ng/108 platelets, p<0.05, for habitual smokers vs controls, 4 and 10 min after the addition of collagen; 0.30±0.15 vs 1.20±0.84 and 0.79±0.50 vs 1.70±0.74 ng/10 8 platelets, p <0.05, after ADP stimulation). Differences were no longer significant 90 min after smoking. Our data indicate that cigarette smoking is associated with platelet dysfunction, which seems due to impairment of metabolic platelet capacity rather than increased platelet activation in vivo.

Molsidomine prevents post-ischaemic ventricular fibrillation in dogs.

Forty anaesthetized dogs were subjected to left circumflex coronary artery ligation followed by reperfusion. Molsidomine was randomly administered to 20 dogs (50 micrograms kg-1 as an i.v. bolus - 15 min prior to coronary occlusion - followed by an infusion of 0.05 micrograms kg-1 min-1. Standard electrocardiographic leads 2 and 3 were continuously recorded to measure ST segment and delta R% changes and to document both the number of ventricular premature beats and the onset of ventricular fibrillation; aortic pressure and cardiac output were measured; thromboxane B2 plasma levels, platelet aggregation produced by ADP, and molsidomine plasma levels were determined before and at 10, 30 and 75 min after the start of the drug protocol. Molsidomine protected the treated animals from early (10 min) post-ischaemic ventricular fibrillation (0 of 20 vs 6 of 20, P = 0.0202), reduced the incidence of overall post-occlusion ventricular fibrillation (3 of 20 vs 10 of 20, P = 0.0407) and improved the total survival rate (P = 0.0067). In molsidomine treated dogs: mean aortic pressure and the rate-pressure product were lowered 10 min after the start of the drug; immediate post-occlusion (3 min) ST segment changes (0.82 +/- 0.52 vs 1.52 +/- 0.78 mV, P less than 0.025) and delta R% changes (37 +/- 50 vs 90 +/- 84%, P less than 0.025) were less marked; the number of ventricular premature beats was lowered and finally, a progressive decline of platelet aggregation produced by ADP was achieved after 75 min of drug infusion. These results were obtained in the presence of mean plasma levels of molsidomine ranging from 20 to 28 ng ml-1. The time-action curve of the antifibrillatory effect of molsidomine parallels those at the level of post-ischaemic electrocardiographic changes.

Cyclooxygenase blockade elevates leukotriene E4 production during acute anaphylaxis in sheep.

We examined changes in the levels of eicosanoids in blood and pulmonary lymph of anesthetized sheep undergoing acute anaphylaxis. Within 1-3 min of intravenous antigenic challenge of previously sensitized sheep, there were approximately 7-30-fold elevations in mean arterial plasma levels of thromboxane B2 and 6-ketoprostaglandin F1 alpha, respectively, as measured by RIA. Negligible changes in levels of these cyclooxygenase products were found in both nonsensitized sheep and in sensitized sheep treated with indomethacin before antigenic challenge. In contrast, no changes in levels of sulfidopeptide leukotrienes (SPLT) in pulmonary lymph were detectable by RIA during anaphylaxis in sensitized or nonsensitized sheep, but levels of SPLT in indomethacin-treated sensitized sheep increased more than fivefold above levels in lymph from both other groups of animals. The immunoreactive SPLT in lymph from indomethacin-treated sheep was accounted for as LTE4, as demonstrated by mobility on HPLC and absorbance at 280 nm. These results support the possibility that certain undesirable effects of nonsteroidal antiinflammatory drugs, such as cardiopulmonary reactions in aspirin-sensitive individuals, and impaired renal and cardiac function during therapy with these drugs, may be related in part to augmented synthesis of the 5-lipoxygenase pathway products, especially those of the sulfidopeptide class. Increased LT production could also limit the antiinflammatory effectiveness of these drugs in many disease states.

Platelet Half-Life, Plasma Thromboxane B2 and Circulating Endothelial-Cells in Peripheral Vascular Disease

We studied platelet half-life (T/2), plasma thromboxane B2-levels (TXB2) and circulating endothelial cells in 107 patients with a mean age of 63 +/- 6.8 years and angiographically proven peripheral vascular disease (PVD). Patients were divided into 4 groups according to Fontaine but also according to additional clinical manifestations of atherosclerosis like coronary heart disease (CHD) and cerebrovascular disease (CVD). Furthermore, the influence of sex and smoking was investigated. Compared to patients without atherosclerotic manifestations we could detect an enhanced platelet consumption measured as shortened platelet half-life time (79.2 +/- 9.1 vs 100.9 +/- 5.6 hours, p less than 0.001 and an increased platelet activity measured as increased TXB2-plasma levels (51.6 +/- 20.9 vs 23.2 +/- 11.2 ng/ml, p less than 0.001). Correspondingly, the amount of circulating endothelial cells was increased 45.2 +/- 25.7 vs 20.3 +/- 23.4, p less than 0.001). Patients with PVD who smoked had the shortest actual platelet half-life, the highest TXB2 plasma levels and the greatest amount of circulating endothelial cells compared to non-smoking patients and controls. Patients with clinical stage IV according to Fontaine had the shortest platelet half-life, the highest TXB2 plasma levels and the greatest amount of circulating endothelial cells compared to the other clinical stages. Analyzing the influence of additional clinical manifestations of atherosclerosis we could detect only in patients with PVD and CHD significant differences compared to the other groups.