thromboxane-b2 and 1-3-dimethylthiourea

We tested the hypothesis that pulmonary hypertension and thromboxane A2 release after heparin neutralization by protamine are mediated by oxygen free radicals. Forty-five pigs in five groups were studied during general anesthesia. Group I animals received 250 IU heparin followed by 100 mg protamine after 15 min. Group II and group III animals received dimethyl sulfoxide (DMSO) and dimethylthiourea (DMTU) 30 min before heparin infusion. Group IV animals were given superoxide dismutase (SOD) 5 min before protamine. Group V served for testing the pulmonary vascular reactivity in DMTU-treated animals to a thromboxane A2 analogue (U-46619). Generation of oxygen free radicals by polymorphonuclear granulocytes (PMNs) was measured in vitro by chemiluminescence. Severe pulmonary hypertension and thromboxane A2 release after protamine were not prevented by either DMSO or SOD. DMTU reduced pulmonary vasoconstriction to U-46619 and protamine but not to TxA2 release, indicating that DMTU had unspecific vascular effects in group III. Heparin-protamine released no oxygen free radicals from isolated PMNs. The results indicate that oxygen free radicals do not have a key role in mediating pulmonary vasoconstriction after protamine neutralization of heparin.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Dimethyl Sulfoxide; Female; Free Radical Scavengers; Hemodynamics; Heparin; Heparin Antagonists; Hypertension, Pulmonary; Leukocyte Count; Leukocytes; Male; Neutrophils; Prostaglandin Endoperoxides, Synthetic; Protamines; Reactive Oxygen Species; Superoxide Dismutase; Swine; Thiourea; Thromboxane B2; Vasoconstrictor Agents

The lung appears to be one of the dominant sites of bacterial clearance from the blood of infant piglets. Part of the lung bacterial clearance involves activation of an oxygen radical bactericidal mechanism that may be central to induction of acute pulmonary hypertension. The present study determined whether this bactericidal activity was intrinsic to resident lung cells. Isolated piglet lung preparations perfused with blood-free salt solution were used to delineate the amount of group B streptococci (GBS) extracted and killed upon transit through pulmonary vasculature. Approximately 45% of infused GBS was deposited in the lung during a single pulmonary transit, whereas nearly 40% of the organisms sequestered in the lung were killed within a 30-min period. Pretreatment with dimethylthiourea, a scavenger of hydroxyl radical that inhibits GBS-induced pulmonary hypertension, attenuated both bacterial uptake and killing to similar extents. Along with its deposition in the lung, GBS also induced concentration-dependent increases in total pulmonary resistance, which were related principally to increases in upstream arterial resistance. Lung weight also increased in a concentration-dependent manner. Both the increase in total pulmonary resistance and lung weight were temporally related to elevation in perfusion medium content of the stable thromboxane degradation product, thromboxane B2. Pretreatment with indomethacin, a prostaglandin H synthase inhibitor, or sodium(E)-3[4-(1-imidazolyl-methyl)phenyl]-2-propenoic acid a thromboxane synthase inhibitor, reduced GBS-induced pulmonary hypertension and edema. These results suggest that, in isolated piglet lungs, GBS evokes an intrinsic bactericidal response residing within lung cells, probably pulmonary intravascular macrophages, which may be responsible for the initiation of pulmonary hemodynamic changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Animals, Newborn; Blood Bactericidal Activity; Hypertension, Pulmonary; In Vitro Techniques; Lung; Pulmonary Circulation; Reactive Oxygen Species; Streptococcal Infections; Streptococcus agalactiae; Swine; Thiourea; Thromboxane B2; Vascular Resistance

Interleukin-2 therapy leads to respiratory dysfunction caused by increased vascular permeability. This study examines the role of oxygen-derived free radicals (OFR). Sheep (n = 6) with chronic lung lymph fistulae were given interleukin-2, 10(5) units/kg, as an intravenous bolus. The mean pulmonary artery pressure rose from 13 to 23 mm Hg (p less than 0.05) at 1 hour and remained elevated for 4 hours, although the pulmonary artery wedge pressure was unchanged at 4 mm Hg. Arterial oxygen tension fell from 88 to 77 mm Hg (p less than 0.05). Lung lymph flow rose from 2.2 to 6.4 ml/30 min (p less than 0.05) at 3 hours. This rise coincided with an increase in the lymph/plasma protein ratio from 0.67 to 0.77 (p less than 0.05) and lymph protein clearance from 1.5 to 4.4 ml/30 min (p less than 0.05), indicating increased lung microvascular permeability. Interleukin-2 led to transient increases in plasma thromboxane B2 from 168 to 388 pg/ml (p less than 0.05) and lung lymph thromboxane B2 from 235 to 694 pg/ml (p less than 0.05). The leukocyte count fell from 8156 to 4375/mm3 (p less than 0.05) primarily caused by a 78% drop in lymphocyte count. Platelet count declined from 292 to 184 X 10(3)/mm3 (p less than 0.05). Pretreatment with the hydroxyl radical scavenger dimethylthiourea, 1 gm/kg, intravenously, (n = 6) prevented the interleukin-2-induced increase in mean pulmonary artery pressure, lung lymph flow, lymph/plasma protein ration, lymph protein clearance, and thromboxane B2 levels in plasma and lung lymph. The arterial oxygen tension decreased from 85 to 80 mm Hg (p less than 0.05). The leukocyte count declined from 7854 to 6229/mm3 (p less than 0.05), but this was not as low nor as prolonged as the interleukin-2 group. Further, the decrease in platelet count was prevented (p less than 0.05). Interleukin-2 incubated with sheep or human leukocytes led to a dose-dependent increase in intracellular hydrogen peroxide production by neutrophils as measured by flow cytometry of dichlorofluorescein oxidation. These data indicate that interleukin-2 stimulates OFR generation and that OFR moderate the interleukin-2-induced increased lung permeability.

Topics: Animals; Blood Pressure; Female; Free Radical Scavengers; Free Radicals; Hydrogen Peroxide; Hypertension, Pulmonary; Interleukin-2; Leukopenia; Lung; Lymph; Oxygen; Platelet Count; Pulmonary Artery; Recombinant Proteins; Sheep; Thiourea; Thromboxane B2

Both thromboxane A2 and oxygen-derived free radicals appear to play central roles in group B streptococcus (GBS)-induced pulmonary hypertension in piglets. This study tested the hypothesis that GBS promotes oxygen radical-dependent thromboxane accumulation and pulmonary hypertension in infant piglets. Piglets 4-12 d old were anesthetized and prepared for assessment of pulmonary arterial pressure and arterial blood gases. In control animals, GBS (10(8) organisms/kg/min for 15 min) increased mean pulmonary artery pressure by 30 +/- 1.5 torr and reduced arterial PO2 by 100 +/- 20 torr. Thromboxane A2, radioimmunoassayed in venous blood as thromboxane B2, increased by 2452 +/- 800 pg/mL. A second group of piglets was treated with dimethylthiourea (DMTU: 750 mg/kg), a putative oxygen radical scavenger. In these animals, GBS increased pulmonary arterial pressure by only 7 +/- 1 torr and reduced arterial PO2 by a modest 10 +/- 8 torr. Importantly, thromboxane B2 content in venous blood failed to increase above control levels in DMTU-treated animals. The protective effects of DMTU in GBS-treated piglets could not be ascribed to inhibition of cyclooxygenase or thromboxane synthase because the oxygen radical scavenger failed to attenuate increases in pulmonary arterial pressure and venous thromboxane B2 content or reductions in arterial PO2 caused by i.v. infusions of arachidonic acid. DMTU also did not ameliorate pulmonary hypertension evoked by the thromboxane mimetic U44069, thereby suggesting that the scavenger did not act as an end-organ antagonist of thromboxane receptors. These observations suggest that GBS promotes accumulation of thromboxane A2 and attendant pulmonary hypertension through an oxygen radical-dependent mechanism.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Free Radicals; Hypertension, Pulmonary; Oxygen; Streptococcal Infections; Streptococcus agalactiae; Swine; Thiourea; Thromboxane B2

Dimethylthiourea (DMTU), a putative hydroxyl radical scavenger, attenuates thromboxane generation and pulmonary hypertension in the piglet model of group B streptococcal (GBS) sepsis. This study tested the hypothesis that DMTU reverses ongoing GBS-induced pulmonary hypertension coincident with decreased thromboxane production. Piglets (n = 15) received a 60 min infusion of GBS (10(-8) cfu/kg/min). Mean pulmonary artery pressure (Ppa), arterial blood gases (ABGs), and thromboxane B2 (TXB) levels were measured at 10 min intervals throughout the study. GBS infusion resulted in a marked increase in pulmonary artery pressure (mean delta Ppa = 31 mm Hg) and a significant decline in PaO2 (mean = -80 torr) within 10 min of beginning the infusion. pH decreased from a mean of 7.47 to 7.37. DMTU, 750 mg/kg, or normal saline vehicle was infused over 10-15 min beginning 10 min after initiating GBS. Ppa decreased significantly within 10 min of DMTU infusion. Piglets receiving vehicle had a slow decline in Ppa. Piglets receiving DMTU also had an improvement in PaO2 and showed no further drop in pH. Piglets receiving vehicle had no improvement in PaO2 and demonstrated a continued decline in pH. TXB levels did not differ between the groups at any time interval. We conclude that DMTU can partially reverse GBS-induced pulmonary hypertension, but may function through mechanisms independent of thromboxane generation.

Topics: Animals; Animals, Newborn; Blood Pressure; Disease Models, Animal; Hypertension, Pulmonary; Oxygen; Partial Pressure; Pulmonary Circulation; Sepsis; Streptococcal Infections; Swine; Thiourea; Thromboxane B2

Treatment with thromboxane (Tx) synthase inhibitors or free radical scavengers has been shown to afford protection from renal ischemia. Since free radicals are closely associated with thromboxane (Tx) synthesis, this study examines the thesis that free radical scavengers inhibit formation of Tx. Anesthetized rats (n = 42) underwent right nephrectomy. By random choice, before 45 min of left renal pedicle clamping, rats received: 0.5 ml dextrose placebo IV (n = 6); the hydroxyl radical scavenger dimethyl-thiourea (DMTU), 500 mg/kg IV (n = 10); or the superoxide scavenger superoxide dismutase (SOD), 24,000 Sigma Units (SU)/kg IV (n = 12). This dose of SOD was repeated before release of the clamp. Treatment with DMTU and SOD decreased plasma TxB2 levels following 5 min of reperfusion from 2,480 pg/ml in dextrose treated controls to 1,155 pg/ml (p less than 0.01) and 1,419 pg/ml (p less than 0.03), respectively. At 24 hr, DMTU and SOD therapy decreased creatinine from 3.0 mg/dl in controls to 1.6 mg/dl (p less than 0.01) and 2.1 mg/dl (p less than 0.05), respectively. At 24 hr, DMTU but not SOD decreased left renal weight from 113 to 94% (p less than 0.0003) of the weight of the previously removed right kidney, and histologically prevented acute tubular necrosis (p less than 0.05). In nephrectomized but nonischemic sham control rats (n = 7) plasma TxB2 and 6-keto-PGF1 alpha concentrations were 757 pg/ml and 82 pg/ml, creatinine level 0.9 mg/dl and kidney weight 94% of the previously removed right kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Ketoprostaglandin F1 alpha; Acute Kidney Injury; Animals; Epoprostenol; Humans; Kidney; Kidney Tubular Necrosis, Acute; Male; Rats; Renal Artery Obstruction; Superoxide Dismutase; Thiourea; Thromboxane B2; Thromboxane-A Synthase

When protamine (2 mg/kg) was injected intravenously into awake sheep 5 minutes after infusing heparin (200 units/kg), there was transient diffuse pulmonary vasoconstriction with mean pulmonary arterial pressure increasing from 18.0 +/- 0.7 to 43.8 +/- 2.7 mm Hg at 1 minute (x +/- SEM; n = 10). In addition, there was profound leukopenia (36.9 +/- 7.7% of baseline values at 2 minutes) with transpulmonary leukocyte sequestration and transiently elevated plasma concentrations of C3a (from 420 +/- 146 to 1,599 +/- 249 ng/ml; n = 3, p less than 0.01) and thromboxane B2 (from 0.30 +/- 0.05 to 6.3 +/- 2.8 ng/ml; n = 10, p less than 0.0001), without significant increases of plasma 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha, leukotrienes, or histamine. Intravenous injection of protamine alone produced no hemodynamic effects and did not increase plasma levels of vasoconstrictor eicosanoids. Intravenous pretreatment with either a cyclooxygenase inhibitor or a hydrogen peroxide scavenger (dimethylthiourea) blocked both the increases of thromboxane levels and the pulmonary vasoconstriction.

Topics: Animals; Arteries; Complement Activation; Dimethyl Sulfoxide; Heparin; Leukocyte Count; Lung; Protamines; Sheep; Thiourea; Thromboxane B2; Thromboxanes; Vasoconstriction

The release of oxygen radicals, in particular the hydroxyl radical, from sequestered neutrophils produces acute lung injury after a number of insults. Our purpose was to determine whether hydroxyl radical, OH., is responsible for the lung injury from endotoxin characterized by (1) pulmonary leukostasis, (2) increased thromboxane production leading to pulmonary hypertension and hypoxia, and (3) increased protein permeability. This hypothesis was tested by infusion of a selective OH. scavenger, dimethyl thiourea (0.75 gm/kg), into unanesthetized sheep before endotoxin and comparison of the response to that seen with endotoxin alone. Pulmonary vascular integrity was measured by the use of lung lymph flow, QL, and lymph protein transport. Thromboxane A2 was measured as TxB2 and prostacyclin as 6-keto-PGF1 alpha. We found no difference in the degree of leukopenia and hypoxia after endotoxin or the levels of TxB2, 6-keto-PGF1 alpha, and pulmonary hypertension with dimethyl thiourea, compared with endotoxin alone. The permeability injury was also identical, with a twofold to threefold increase in protein-rich lymph seen in both groups. It appears that OH. does not play a major causative role in either phase of endotoxin lung injury.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Capillary Permeability; Endotoxins; Escherichia coli; Free Radicals; Hemodynamics; Hydroxides; Hydroxyl Radical; Lung; Lymph; Neutrophils; Proteins; Sheep; Thiourea; Thromboxane B2