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C Thiemermann

Publications and source records attributed to C Thiemermann.

At least 145 records · Page 8Linked to original sources
PubMed1994

Invited opinion: role of nitric oxide in hemorrhagic, traumatic, and anaphylactic shock and thermal injury.

The free radical nitric oxide (NO) is synthesized from the guanidino group of L-arginine by a family of enzymes termed NO synthase (NOS). Hemorrhagic shock leads to an inhibition of NO production by the calcium-dependent, endothelial NOS (ecNOS), which may lead to maldistribution of blood flow leading to, e.g., coronary, renal, and cerebral ischemia and may enhance the adhesion of neutrophil granulocytes and platelets to the endothelial surface. Prolonged periods of hemorrhagic shock are associated with the induction of a calcium-independent isoform of NOS in a variety of organs and in the vascular smooth muscle. The formation of large quantities of NO by inducible isoform of NOS (iNOS) contributes to the delayed vascular decompensation and to the hyporeactivity of the vasculature to vasoconstrictor agents. An impairment of NO formation by the ecNOS has been demonstrated in various models of traumatic shock, whereas there is good experimental evidence supporting the hypothesis that an enhanced formation of NO contributes to the pathophysiology of experimental thermal injury and anaphylactic shock. We speculate that a pharmacological modulation of NO biosynthesis which either enhances NO concentration in the vicinity of endothelium (i.e., NO donors) or inhibits NO overproduction following iNOS expression (i.e., iNOS-selective NOS inhibitors) may become novel therapies to improve the outcome of patients with circulatory shock of various etiologies.

Amino Acid Oxidoreductases↗
PubMed1993

Selectivity of nonsteroidal antiinflammatory drugs as inhibitors of constitutive and inducible cyclooxygenase.

Constitutive cyclooxygenase (COX-1; prostaglandin-endoperoxide synthase, EC 1.14.99.1) is present in cells under physiological conditions, whereas COX-2 is induced by some cytokines, mitogens, and endotoxin presumably in pathological conditions, such as inflammation. Therefore, we have assessed the relative inhibitory effects of some nonsteroidal antiinflammatory drugs on the activities of COX-1 (in bovine aortic endothelial cells) and COX-2 (in endotoxin-activated J774.2 macrophages) in intact cells, broken cells, and purified enzyme preparations (COX-1 in sheep seminal vesicles; COX-2 in sheep placenta). Similar potencies of aspirin, indomethacin, and ibuprofen against the broken cell and purified enzyme preparations indicated no influence of species. Aspirin, indomethacin, and ibuprofen were more potent inhibitors of COX-1 than COX-2 in all models used. The relative potencies of aspirin and indomethacin varied only slightly between models, although the IC50 values were different. Ibuprofen was more potent as an inhibitor of COX-2 in intact cells than in either broken cells or purified enzymes. Sodium salicylate was a weak inhibitor of both COX isoforms in intact cells and was inactive against COX in either broken cells or purified enzyme preparations. Diclofenac, BW 755C, acetaminophen, and naproxen were approximately equipotent inhibitors of COX-1 and COX-2 in intact cells. BF 389, an experimental drug currently being tested in humans, was the most potent and most selective inhibitor of COX-2 in intact cells. Thus, there are clear pharmacological differences between the two enzymes. The use of such models of COX-1 and COX-2 activity will lead to the identification of selective inhibitors of COX-2 with presumably less side effects than present therapies. Some inhibitors had higher activity in intact cells than against purified enzymes, suggesting that pure enzyme preparations may not be predictive of therapeutic action.

Animals↗
PubMed1993

Interleukin-1 contributes to the induction of nitric oxide synthase by endotoxin in vivo.

We investigated the role of interleukin-1 in the induction of a Ca(2+)-independent nitric oxide (NO) synthase by bacterial endotoxin in vivo. In anaesthetized rats, pretreatment with interleukin-1 receptor antagonist (interleukin-1ra; 16 mg kg-1 i.v., followed by an infusion of 2.4 mg kg-1 h-1) ameliorated the delayed hypotension and tachycardia in response to endotoxin (2 mg kg-1 i.v.). Endotoxaemia for 3 h induced a Ca(2+)-independent NO synthase activity in the lung and reduced the contractions to noradrenaline in the thoracic aorta ex vivo. Treatment with interleukin-1ra attenuated both the induction of NO synthase in the lung (by 46 +/- 5%) and the endotoxin-induced hyporeactivity to noradrenaline in the aorta. Thus, endogenous interleukin-1 contributes to the induction of NO synthase in response to endotoxin in vivo.

Amino Acid Oxidoreductases↗
PubMed1993

Dihydropyridine antagonists and agonists of calcium channels inhibit the induction of nitric oxide synthase by endotoxin in cultured macrophages.

Here we investigate the effects of the dihydropyridine-type antagonists of calcium channels nitrendipine, nimodipine, nisoldipine and the calcium channel agonist BAY K 8644 on the induction of nitric oxide synthase (NOS) by bacterial endotoxin (lipopolysaccharide; LPS) in J774.2 macrophages cultured in vitro. Pretreatment of J774.2 cells with these dihydropyridines (10(-8) -3 x 10(-6) M for 30 min) dose-dependently inhibited the LPS-stimulated (1 microgram/ml, 24 h) nitrite formation. For instance, at 10(-6) M, the inhibition was 59 +/- 3% for nitrendipine; 47 +/- 5% for nimodipine and 42 +/- 3% for nisoldipine (n = 9; p < 0.05). BAY K 8644 caused a moderate, but significant inhibition of nitrite accumulation (by 16 +/- 3% at 10(-7) M, n = 9; p < 0.05). The inhibition of LPS-stimulated nitrite accumulation produced by nitrendipine, nimodipine, and BAY K 8644 was significantly smaller when they were applied 2 or 4 h after LPS, indicating that these agents inhibit the induction, but not the activity of the induced NOS. At concentrations which caused a significant inhibition of the LPS-stimulated nitrite accumulation, the dihydropyridine calcium channel modulators did not inhibit mitochondrial respiration. Thus, dihydropyridine calcium channel modulators (antagonists and an agonist) inhibit the induction of the calcium-independent isoform of NOS produced by LPS in J774.2 macrophages. This effect is not related to the modulation of intracellular calcium levels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1993

Inhibition of the production of nitric oxide and vasodilator prostaglandins attenuates the cardiovascular response to bacterial endotoxin in adrenalectomized rats.

Bacterial lipopolysaccharide (LPS) is the toxic moiety of the gram-negative bacterial outer membrane which is responsible for many of the pathophysiological events that occur during endotoxic shock. Here we investigate the hypothesis that endogenous glucocorticoids modulate the formation of nitric oxide (NO) and of vasodilator cyclooxygenase metabolites in response to LPS. Intravenous administration of a small dose of Escherichia coli LPS (0.1 mg kg-1) to normal Wistar rats caused a moderate fall in blood pressure, and 120 min of endotoxaemia was not associated with an attenuation of the rise in blood pressure elicited by intravenous injection of noradrenaline (NA; vascular hyporeactivity). When adrenalectomized (ADX) rats, which lack endogenous glucocorticoids, were subjected to the same dose of LPS, they developed a much more severe form of circulatory shock, which was characterized by a profound fall in blood pressure and a vascular hyporeactivity to NA. Both hypotension and vascular hyporeactivity were prevented by pre-treatment with dexamethasone. Inhibition of NO biosynthesis with NG-methyl-L-arginine significantly attenuated the hypotension and the vascular hyporeactivity to NA caused by LPS in ADX rats. Similarly, the cyclooxygenase inhibitor indomethacin significantly attenuated the circulatory failure elicited by LPS in the ADX rats. Interestingly, 120 min of endotoxaemia resulted in a de novo biosynthesis of an induced isoform of NO synthase in the lungs of ADX, but not normal Wistar, rats. This induction of NO synthase was prevented by dexamethasone pre-treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1993

Modification of energy metabolism and radiation response of a murine tumour by changes in nitric oxide availability.

The nitric oxide donor, SIN-1 and nitric oxide synthase inhibitor, nitro-L-arginine were examined for their effects on energy metabolism using 31P magnetic resonance spectroscopy, and on radiation sensitivity in the transplantable murine tumour, SCCVII/Ha. SIN-1 at 2 mg/kg i.v. reduced Pi/total by 40-50% within 10 min and increased X-ray sensitivity 3 fold, consistent with increased tumour oxygenation. Nitro-L-arginine at 10 mg/kg i.v. increased Pi/total by 250% at 45 min and was maintained for at least 2 hr. Nitro-L-arginine also increased radiation resistance 3-5 fold, consistent with the induction of tumour hypoxia. The results indicate that tumour energy metabolism may be altered through drug induced modification of nitric oxide availability, and that these changes are sufficient to modify tumour sensitivity to X-rays.

Animals↗
PubMed1993

Vascular hyporeactivity to vasoconstrictor agents and hemodynamic decompensation in hemorrhagic shock is mediated by nitric oxide.

This study investigates the role of nitric oxide (NO) and the induction of a calcium-independent NO synthase (NOS) in development of vascular hyporeactivity to norepinephrine (NE) and vascular decompensation associated with hemorrhagic shock (HS) in the anesthetized rat. HS for 120 min caused a time-dependent reduction of the pressor responses to NE. This hyporeactivity is mediated by an enhanced release of NO by the constitutive NOS, for it was reversed by NG-nitro-L-arginine methyl ester (NO2Arg), an inhibitor of both constitutive and inducible NOS, but it was not prevented by dexamethasone, an inhibitor of NOS induction. Vascular decompensation following prolonged periods of HS was characterized by a failure of control animals to maintain arterial blood pressures despite reinfusion of blood. This progressive decrease in blood pressure is mediated by enhanced formation of NO by the inducible NOS, for it was prevented by NO2Arg or dexamethasone. A strong increase in calcium-independent (inducible) NOS activity was observed in several organs after 150 and 330 min of HS, being most pronounced in lung, liver, and spleen. HS for 330, but not 150, min also caused hyporeactivity of rat aortic rings to vasoconstrictors, which was associated with induction of calcium-independent NOS activity in this tissue. Aortic hyporeactivity was prevented by dexamethasone pretreatment in vivo and reversed by NO2Arg in vitro. HS was not associated with an increase in plasma endotoxin levels, showing that endotoxin does not account for induction of NOS in this model. Thus, excessive NO formation induces vascular hyporeactivity and decompensation in HS, indicating that NOS inhibitors, particularly of the inducible NOS, may improve the therapeutic outcome of patients suffering from HS.

Amino Acid Oxidoreductases↗
PubMed1993

Vasoconstriction in the rat kidney induced by endothelin-1 is blocked by PD 145065.

We have previously shown that the receptors mediating the renal and systemic vasoconstrictor effects of endothelin-1 (ET-1) are of two distinct endothelin receptor subtypes. Here, we evaluate the effect of PD 145065, a nonselective endothelin receptor antagonist, on the renal vasoconstrictor effects of ET-1 in the rat kidney. ET-1 induced concentration-dependent increases in perfusion pressure in the isolated perfused kidney of the rat. The ETA receptor-selective antagonists BQ-123 (10 microM) and FR 139317 (10 microM) lowered the ET-1-induced rise in perfusion pressure by 57% and 61%, respectively, at 3 x 10(-10) M ET-1. By comparison, the ET-1-induced vasoconstriction was fully antagonized (96% inhibition) by PD 145065 (10 microM). In the anesthetized rat, ET-1 produced a dose-dependent increase in mean arterial pressure, which was attenuated by PD 145065. The initial depressor response to ET-1 was completely blocked by PD 145065, as were the reduction in renal blood flow and increase in renal vascular resistance induced by ET-1. These results suggest that both the ETA and a non-ETA receptor subtype play an important role in mediating the vasoconstrictor effects of ET-1 in the rat kidney.

Amino Acid Sequence↗
PubMed1993

Heterogeneous receptors mediate endothelin-1-induced changes in blood pressure, hematocrit, and platelet aggregation.

Using selective endothelin (ET) receptor antagonists, we investigated which ET receptor subtypes mediate the changes in blood pressure and hematocrit produced by intraarterial injection of ET-1 in the anesthetized rabbit. In addition, the receptor through which ET-1 stimulates the release of prostacyclin (PGI2) and, hence, inhibits ex vivo platelet aggregation, was identified. FR 139317 (ETA antagonist, 0.6 mg kg-1 min-1 preceded by a loading dose of 3 mg kg-1 i.v.) and PD 145065 (nonselective ETA/ETB antagonist, 0.6 mg kg-1 min-1 preceded by a loading dose of 3 mg kg-1 i.v.) attenuated the ET-1 (1 nmol kg-1 i.a.)-induced rise in mean arterial pressure (MAP) by 89% and 75%, respectively. In contrast to FR 139317, PD 145065 also abolished the initial, transient depressor response brought about by ET-1. ET-1 caused a significant increase in hematocrit 15 min after its injection. PD 145065 caused a significantly greater inhibition of this hemoconcentration than FR 139317. ET-1 inhibited ex vivo platelet aggregation by 96%, measured 5 min after injection of the peptide. PD 145065, but not FR 139317, abolished the antiaggregatory effects of ET-1. Thus, the ET-1-induced vasoconstriction in the anesthetized rabbit is predominantly mediated via the ETA receptor, whereas the depressor and antiaggregatory actions of ET-1 are caused by activation of the ETB receptor. Moreover, activation of both receptor subtypes by ET-1 accounts for the increase in hematocrit produced by ET-1 in vivo.

Animals↗
PubMed1993

Incomplete inhibition of the pressor effects of endothelin-1 and related peptides in the anaesthetized rat with BQ-123 provides evidence for more than one vasoconstrictor receptor.

1. The effects of the ETA receptor antagonist, BQ-123 on blood pressure changes induced by various members of the endothelin (ET)/sarafotoxin (SX) peptide superfamily were investigated in the anaesthetized rat. 2. ET-1 (1 nmol kg-1, i.v. bolus) induced a sustained increase in mean arterial pressure (MAP, maximum increase 44 +/- 3 mmHg). Intravenous injection of BQ-123 at 0.2, 1.0 or 5.0 mg kg-1 5 min before ET-1 inhibited the pressor response by 18, 50 and 61%, respectively. The ET-1 pressor response was inhibited by 75% when the peptide was given 60 min after the start of a 120 min i.v. infusion of BQ-123 (0.2 mg kg-1 min-1). 3. In addition to ET-1, BQ-123 (1 mg kg-1, i.v. bolus) attenuated the pressor responses to big ET-1 (1 nmol kg-1, i.v., bolus, maximum increase in MAP: 68 +/- 7 mmHg), ET-3 (3 nmol kg-1, i.v., bolus, maximum response: 30 +/- 3 mmHg), SX6b (1 nmol kg-1, i.v., bolus, maximum response: 41 +/- 5 mmHg) and SX6c (1 nmol kg-1, i.v., bolus, maximum response: 24 +/- 4 mmHg) by 65, 60, 88 and 50%, respectively. 4. With the exception of big ET-1, all the peptides used in this study induced an initial transient depressor response (-32 +/- 3 mmHg, n = 18). Although BQ-123 (1 mg kg-1, i.v., bolus) did not affect the absolute magnitude of the fall in MAP, the ETA receptor antagonist significantly prolonged the depressor responses induced by ET-3 and SX6b. 5. Thus, BQ-123 attenuates the pressor, but not the depressor effects of ET-1, big ET-1, ET-3, SX6b and SX6c. Complete inhibition of the pressor responses could not be achieved, suggesting that a component of the pressor response is not mediated via the ETA receptor.

Amino Acid Sequence↗
PubMed1993

Mediation via different receptors of the vasoconstrictor effects of endothelins and sarafotoxins in the systemic circulation and renal vasculature of the anaesthetized rat.

1. Using endothelin-1 (ET-1), endothelin-3 (ET-3), sarafotoxin 6b (SX6b) and sarafotoxin 6c (SX6c) as agonists and BQ-123 as a selective ETA receptor antagonist, we have examined the endothelin receptor subtypes mediating the systemic pressor and renal vasoconstrictor effects of the ET/SX family of peptides. 2. In anaesthetized rats, bolus intravenous injections of ET-1, ET-3, SX6b or SX6c (0.1, 0.25 and 0.50 nmol kg-1) produced initial transient depressor responses followed by sustained and dose-dependent increases in mean arterial pressure (MAP) with the following rank order of potency: SX6b > ET-1 >> SX6c > ET-3. In contrast, in the renal vasculature these peptides caused equipotent dose-dependent falls in renal blood flow (RBF) (ET-1 = ET-3 = SX6b = SX6c). 3. BQ-123 (1 mg kg-1, i.v. bolus) significantly reduced the systemic pressor effects of all the peptides but was largely ineffective against the renal vasoconstrictions. 4. These results indicate that although the systemic pressor effects of the ET/SX peptides are mediated via ETA receptors, the vasoconstriction in the kidney in vivo may be mediated predominantly via ETB-like receptors. This may be of therapeutic relevance, for an ETA-receptor-selective antagonist could offer only poor protection of the renal circulation from the deleterious effects of endogenously produced members of this peptide family.

Anesthesia↗
PubMed1993

Nitric oxide-mediated hyporeactivity to noradrenaline precedes the induction of nitric oxide synthase in endotoxin shock.

1. The role of an enhanced formation of nitric oxide (NO) and the relative importance of the constitutive and inducible NO synthase (NOS) for the development of immediate (within 60 min) and delayed (at 180 min) vascular hyporeactivity to noradrenaline was investigated in a model of circulatory shock induced by endotoxin (lipopolysaccharide; LPS) in the rat. 2. Male Wistar rats were anaesthetized and instrumented for the measurement of mean arterial blood pressure (MAP) and heart rate. In addition, the calcium-dependent and calcium-independent NOS activity was measured ex vivo by the conversion of [3H]-arginine to [3H]-citrulline in homogenates from several organs obtained from vehicle- and LPS-treated rats. 3. E. coli LPS (10 mg kg-1, i.v. bolus) caused a rapid (within 5 min) and sustained fall in MAP. At 30 and 60 min after LPS, pressor responses to noradrenaline (0.3, 1 or 3 micrograms kg-1, i.v.) were significantly reduced. The pressor responses were restored by NG-nitro-L-arginine methyl ester (L-NAME, 1 mg kg-1, i.v. at 60 min), a potent inhibitor of NO synthesis. In contrast, L-NAME did not potentiate the noradrenaline-induced pressor responses in control animals. 4. Dexamethasone (3 mg kg-1, i.v., 60 min prior to LPS), a potent inhibitor of the induction of NOS, did not alter initial MAP or pressor responses to noradrenaline in control rats, but significantly attenuated the LPS-induced fall in MAP at 15 to 60 min after LPS. Dexamethasone did not influence the development of the LPS-induced immediate (within 60 min) hyporeactivity to noradrenaline. However,dexamethasone pretreatment prevented the hypotension and vascular hyporeactivity at 180 min.5. At 60 min after LPS a moderate increase in the activity of a calcium-independent (inducible) NOS activity was detected in the aorta, but not in any of the other tissues studied. However, at 180 min after LPS, a significant NOS induction was observed in the lung, liver, spleen, mesentery, heart and aorta.This NOS induction was substantially prevented by pretreatment with dexamethasone.6. These results suggest that the immediate hypotension and vascular hyporeactivity to noradrenaline in endotoxin shock is caused by an enhanced formation of NO due to activation of the constitutive enzyme. The delayed hypotension and vascular hyporeactivity, however, is due to enhanced NO formation by the LPS-induced enzyme.

Amino Acid Oxidoreductases↗
PubMed1993

Support of renal blood flow after ischaemic-reperfusion injury by endogenous formation of nitric oxide and of cyclo-oxygenase vasodilator metabolites.

1. Ischaemia-reperfusion injury in the kidney is associated with a loss of autoregulation, an increase in renal vascular resistance (RVR), a decrease of renal blood flow (RBF) and ultimately acute renal failure. The aim of this study was to investigate the role of the release of endogenous nitric oxide (NO) in the recovery of RBF after ischaemic injury of the renal vascular bed. 2. Anaesthetized rats (thiopentone sodium; 120 mg kg-1, i.p.) were submitted to acute renal ischaemia followed by 2 or 6 h of reperfusion (I/R). Reperfusion was associated with a significant reduction in RBF, an increase in RVR, and an impairment of the vasodilator effect of acetylcholine (ACh). 3. NG-nitro-L-arginine methyl ester (L-NAME, 30 micrograms kg-1 min-1, i.v., n = 5) significantly prevented the recovery of RBF after I/R injury. Similarly, inhibition of prostanoid formation with indomethacin (5 mg kg-1, i.v., n = 4) significantly enhanced the rise in RVR associated with I/R injury. 4. Infusion of L-arginine (L-Arg; 1 or 3 mg kg-1 min-1, i.v., n = 5 and 4, respectively) or D-Arg (1 mg kg-1 min-1, i.v., n = 6), starting 30 min after occlusion, did not improve the recovery of RBF. Furthermore, infusion of L-Arg (20 mg kg-1 min-1 for 15 min; n = 4) had no effect on the I/R-induced impairment of the vasodilator responses to ACh. 5. To elucidate the relative importance of the constitutive and inducible NO synthase isoforms for the formation of NO after I/R, calcium-dependent (constitutive) and calcium-independent (inducible) NO synthase activities were measured in kidney homogenates obtained from ischaemic or non-ischaemic kidneys. A calcium-independent NO synthase activity was not detectable in kidney homogenates obtained from either sham-operated control rats or from animals subjected to I/R. Moreover, dexamethasone(3 mg kg-1, i.v., 60 min prior to I/R, n = 6), an inhibitor of the induction of NO synthase,had no effect on either RBF or RVR in rats subjected to I/R. In contrast to I/R, lipopolysaccaride(LPS, endotoxin; 5 mg kg-1, i.p., n = 3) caused a significant induction of a calcium-independent NO synthase activity in the kidney.6. These results confirm the importance of the release of vasodilator cyclo-oxygenase metabolites in the compromised renal circulation and indicate that the formation of NO derived from the constitutive, but not the inducible NO synthase, is also important for the maintenance of RBF after I/R injury of the renal vascular bed.

Amino Acid Oxidoreductases↗
PubMed1993

Mediation of endothelin-1-induced inhibition of platelet aggregation via the ETB receptor.

1. The effects of FR139317 (ETA antagonist) or PD145065 (non-selective ETA/ETB antagonist) on endothelin-1 (ET-1)-induced changes in blood pressure and inhibition of ex vivo platelet aggregation were investigated in the anaesthetized rabbit. 2. ET-1 (1 nmol kg-1, i.a. bolus) caused a sustained increase in mean arterial pressure (MAP) (peak increase 47 +/- 5 mmHg, n = 8). Intravenous infusion of FR139317 at 0.2 (n = 4) or 0.6 mg kg-1 min-1 (n = 4) inhibited the ET-1 pressor response by 83 or 89%, respectively. Infusion of PD145065 at 0.2 (n = 4) or 0.6 mg kg-1 min-1 (n = 4) inhibited the ET-1-induced increase in MAP by 79 or 75%, respectively. 3. The transient depressor response (-16 +/- 3 mmHg) which preceded the rise in blood pressure induced by ET-1 (1 nmol kg-1, i.a., n = 8) was enhanced by an intravenous infusion of FR139317 (0.6 mg kg-1 min-1) to -35 +/- 5 mmHg (P < 0.05, n = 4). This enhancement was abolished by indomethacin (5 mg kg-1, i.v.) pretreatment (-17 +/- 1 mmHg, n = 4). PD145065 (0.2 mg kg-1 min-1, i.v.) attenuated the ET-1-induced fall in blood pressure to -9 +/- 1 mmHg (n = 4), while a higher dose of this antagonist (0.6 mg kg-1 min-1, i.v.) completely abolished the ET-1-mediated depressor response. 4. ET-1 (1 nmol kg-1, n = 8) inhibited ex vivo platelet aggregation by 96% at 5 min after injection of the peptide. FR139317 (0.2 or 0.6 mg kg-1 min-1, i.v.) or PD145065 (0.2mg kg-1 min-1, i.v.) did not affect the inhibition of ex vivo platelet aggregation in response to ET-1. In contrast, intravenous infusion of PD145065 (0.6 mg kg-1 min-1) abolished the anti-aggregatory effects of ET-1.5. Thus, FR139317 inhibits the pressor, but not the depressor actions of ET-1 and has no effect on the ET-l-induced inhibition of ex vivo platelet aggregation. In contrast, PD145065 antagonizes the pressor and depressor responses to ET-1 and abolishes the anti-aggregatory effects of the peptide.6. These results strongly suggest that ET-1-induced vasoconstriction in the anaesthetized rabbit is primarily mediated via the ETA receptor while the depressor and antiaggregatory actions of ET-1 are due to activation of the ETB receptor.

Animals↗
PubMed1993

Role of tumour necrosis factor in the induction of nitric oxide synthase in a rat model of endotoxin shock.

1. This study investigates the role of tumour necrosis factor (TNF) in the induction of nitric oxide synthase (NOS) by bacterial endotoxin (lipopolysaccharide; LPS) in a rat model of endotoxin shock. 2. In anaesthetized rats, pretreatment with a monoclonal antibody for TNF (TNFab; 20 mg kg-1, s.c., at 16 h prior to LPS) ameliorated the fall in mean arterial blood pressure (MAP) in response to LPS (2 mg kg-1, i.v.). For instance, endotoxaemia for 180 min resulted in a fall in MAP from 114 +/- 6 (control) to 84 +/- 5 mmHg (P < 0.01; n = 7). In contrast, animals pretreated with TNFab prior to LPS injection maintained significantly higher MAP when compared to LPS-control (MAP at 180 min; 118 +/- 3 mmHg; P < 0.01, n = 5). 3. Three hours of endotoxaemia was also associated with a significant reduction of the contractile effects of noradrenaline (NA) (10(-8)-10(-6) M) on the thoracic aorta ex vivo. This hyporeactivity to NA was partially restored by in vitro treatment of the vessels with NG-nitro-L-arginine methyl ester (L-NAME, 20 min, 3 x 10(-4) M). Pretreatment of rats with TNFab (20 mg kg-1; at 16 h prior to LPS) significantly (P < 0.05) attenuated the LPS-induced hyporeactivity of rat aortic rings ex vivo. L-NAME did not enhance the contractions of aortic rings obtained from TNFab pretreated LPS-rats. 4. At 180 min after LPS there was a significant elevation of the induced NOS activity in the lung (5.14 +/- 0.57 pmol citrulline mg-1 min-1, n = 8). TNFab pretreatment significantly attenuated this induction of NOS in response to LPS by 37 +/- 6% (n = 5; P<0.05).5. We conclude that the formation of endogenous TNF contributes to the induction of the calcium in dependent isoform of NOS in response to LPS in vivo. Thus, the beneficial effects of agents which inhibit either the release or the action of TNF in circulatory shock may be, in part, due to inhibition of NOS induction.

Amino Acid Oxidoreductases↗
PubMed1993

Platelet-activating factor contributes to the induction of nitric oxide synthase by bacterial lipopolysaccharide.

This study investigates the role of endogenous platelet-activating factor (PAF) in the production of nitric oxide (NO) by constitutive and inducible isoforms of NO synthase (NOS) in endotoxin shock. In anesthetized rats, 3 hours of endotoxemia resulted in a fall in mean arterial blood pressure (MAP) from 127 +/- 5 (control) to 61 +/- 7 mm Hg and a reduction of the pressor responses to norepinephrine (NE, 1 microgram.kg-1) from 33 +/- 3 (control) to 17 +/- 2 mm Hg. Endotoxemia for 3 hours also resulted in a significant reduction in the contractile effects of NE (10(-8) to 10(-6) mol/L) in thoracic aortas ex vivo. This hyporeactivity to NE was due to an enhanced formation of NO, for it was restored by the NOS inhibitor NG-nitro-L-arginine methyl ester. Animals pretreated with the PAF receptor antagonist WEB 2086 maintained higher MAP (MAP at 180 minutes, 98 +/- 6 mm Hg) and exhibited more pronounced pressor responses to NE at 180 minutes after LPS injection. Moreover, WEB 2086 attenuated by 58% the lipopolysaccharide (LPS)-induced hyporeactivity of the rat aortic rings ex vivo. At 3 hours after LPS injection, calcium-independent NOS activity was induced in the lung. The activity of inducible NOS was significantly lower (by 31%) in lungs of rats pretreated with WEB 2086. The hypothesis that WEB 2086 attenuates the induction of NOS in vivo was substantiated in vitro by the finding that pretreatment with WEB 2086 for 30 minutes inhibited the LPS-stimulated NO production in cultured murine macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1993

Nifedipine inhibits the induction of nitric oxide synthase by bacterial lipopolysaccharide.

We investigated the effect of the calcium channel antagonist nifedipine on the induction of nitric oxide synthase (NOS) by bacterial endotoxin (lipopolysaccharide; LPS) in J774.2 macrophages, in cultured rat aortic smooth muscle cells and in a rat model of endotoxin shock. Stimulation by LPS for 24 hr increased nitrite accumulation in the supernatant of both cell types. NOS induction accounts for this nitrite accumulation, as both NG-methyl-L-arginine and cycloheximide reduced nitrite production in both cell types. Dexamethasone inhibited LPS-stimulated nitrite production in macrophages, but not in rat aortic smooth muscle cells. Nifedipine inhibited the production of nitrite in these LPS-treated cell types, with a more pronounced effect on macrophages. However, nifedipine did not inhibit the production of nitrite in J774.2 cells in which NOS had already been induced by prior exposure to LPS, and any possible further induction was inhibited by cycloheximide. In anesthetized rats subjected to LPS, pretreatment with nifedipine or dexamethasone ameliorated the fall in mean arterial blood pressure and the vascular hyporeactivity to norepinephrine at 180 min after LPS injection. At 180 min after LPS, an increase in a calcium-independent (induced) NOS activity was measured in lung homogenates. This induced NOS activity was reduced in lungs from rats treated with nifedipine or dexamethasone before LPS. Thus, nifedipine inhibits the induction of NOS in response to LPS in cultured cells in vitro and in the anesthetized rat.

Amino Acid Oxidoreductases↗