51
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Armstead WM. Vasopressin induced cyclooxygenase dependent superoxide generation contributes to K(+) channel function impairment after brain injury. Brain Res 2001; 910:19-28. [PMID: 11489250 DOI: 10.1016/s0006-8993(01)02716-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
This study determined if vasopressin generates superoxide anion (O2(-)) in a cyclooxygenase dependent manner and if such production contributes to impairment of dilation to activators of ATP sensitive K(+) (K(ATP)) and calcium sensitive K(+) (K(ca)) channels following fluid percussion brain injury (FPI) in newborn pigs equipped with closed cranial windows. Superoxide dismutase (SOD) inhibitable nitroblue tetrazolium (NBT) reduction was determined as an index of O2(-) generation. Under non-brain injury conditions, topical vasopressin (40 pg/ml, the concentration present in CSF following FPI) increased SOD inhibitable NBT reduction from 1+/-1 to 25+/-4 pmol/mm(2). Indomethacin, a cyclooxygenase inhibitor, blunted such NBT reduction (1+/-1 to 5+/-1 pmol/mm(2)), while the vasopressin antagonist, l-(beta-mercapto-beta beta-cyclopentamethylene propionic acid) 2-(o-methyl)-Tyr-AVP (MEAVP) blocked NBT reduction. MEAVP and indomethacin also blunted the NBT reduction observed after FPI. Under non-brain injury conditions, vasopressin (40 pg/ml) coadministered with the K(ATP) and K(ca) channel agonists, cromakalim and NS1619 (10(-8), 10(-6) M) diminished dilation to these K(+) channel agonists while indomethacin partially prevented such impairment (13+/-1 and 23+/-1 vs. 4+/-1 and 10+/-2 vs. 8+/-1 and 19+/-1% for cromakalim in untreated, vasopressin, and vasopressin plus indomethacin treated piglets, respectively). Cromakalim and NS1619 induced pial artery dilation was attenuated following FPI, while indomethacin or MEAVP preadministration partially prevented such impairment (13+/-1 and 23+/-1, sham control; 1+/-1 and 4+/-1, FPI; 8+/-1 and 16+/-3%, FPI-indomethacin pretreated for responses to cromakalim 10(-8), 10(-6) M, respectively). These data show that vasopressin increased O2(-) production in a cyclooxygenase dependent manner and contributed to this production after FPI. These data also show that vasopressin blunted K(ATP) and K(ca) channel mediated cerebrovasodilation in a cyclooxygenase dependent manner. These data suggest that vasopressin induced cyclooxygenase dependent O2(-) generation contributes to K(ATP) and K(ca) channel function impairment after FPI.
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Affiliation(s)
- W M Armstead
- Department of Anesthesia, University of Pennsylvania, Philadelphia, PA 19104, USA.
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52
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Morawietz H, Weber M, Rueckschloss U, Lauer N, Hacker A, Kojda G. Upregulation of vascular NAD(P)H oxidase subunit gp91phox and impairment of the nitric oxide signal transduction pathway in hypertension. Biochem Biophys Res Commun 2001; 285:1130-5. [PMID: 11478771 DOI: 10.1006/bbrc.2001.5312] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this study we analyzed the role of vascular NAD(P)H oxidase in the generation of O(2)(-) and the endothelial impairment of NO signal transduction pathway in hypertension. In aortic rings of 15-month-old stroke-prone spontaneously hypertensive rats (SHR15) we found a 10-fold increased expression of NAD(P)H oxidase subunit gp91phox mRNA associated with a 3-fold increased production of O(2)(-) compared to age-matched Wistar rats (WIS15). Vasorelaxation studies in aortas of SHR15 showed a strongly diminished response to acetylcholine, NO-donor S-nitroso-N-acetyl-d,l-penicillamine, and organic nitrate glyceryl trinitrate compared to WIS15. Soluble guanylate cyclase (sGC) activity and sGC beta(1)-subunit protein expression was downregulated in aortas and lungs of SHR15. These data suggest an upregulation of vascular NAD(P)H oxidase and an impairment of the NO signal transduction pathway in hypertension.
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Affiliation(s)
- H Morawietz
- Institute of Pathophysiology, Martin Luther University Halle-Wittenberg, Halle, Germany
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53
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Harris AP, Robinson R, Koehler RC, Traystman RJ, Gleason CA. Blood-brain barrier permeability during dopamine-induced hypertension in fetal sheep. J Appl Physiol (1985) 2001; 91:123-9. [PMID: 11408422 DOI: 10.1152/jappl.2001.91.1.123] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dopamine is often used as a pressor agent in sick newborn infants, but an increase in arterial blood pressure could disrupt the blood-brain barrier (BBB), especially in the preterm newborn. Using time-dated pregnant sheep, we tested the hypothesis that dopamine-induced hypertension increases fetal BBB permeability and cerebral water content. Barrier permeability was assessed in nine brain regions, including cerebral cortex, caudate, thalamus, brain stem, cerebellum, and spinal cord, by intravenous injection of the small tracer molecule [(14)C]aminoisobutyric acid at 10 min after the start of dopamine or saline infusion. We studied 23 chronically catheterized fetal sheep at 0.6 (93 days, n = 10) and 0.9 (132 days, n = 13) gestation. Intravenous infusion of dopamine increased mean arterial pressure from 38 +/- 3 to 53 +/- 5 mmHg in 93-day fetuses and from 55 +/- 5 to 77 +/- 8 mmHg in 132-day fetuses without a decrease in arterial O(2) content. These 40% increases in arterial pressure are close to the maximum hypertension reported for physiological stresses at these ages in fetal sheep. No significant increases in the brain transfer coefficient of aminoisobutyric acid were detected in any brain region in dopamine-treated fetuses compared with saline controls at 0.6 or 0.9 gestation. There was also no significant increase in cortical water content with dopamine infusion at either age. We conclude that a 40% increase in mean arterial pressure during dopamine infusion in normoxic fetal sheep does not produce substantial BBB disruption or cerebral edema even as early as 0.6 gestation.
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Affiliation(s)
- A P Harris
- Department of Anesthesiology/Critical Care Medicine, The Johns Hopkins University, Baltimore, Maryland 21287, USA
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54
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Satoh M, Mashino T, Nagano T, Hirobe M, Takayanagi I, Koike K. INHIBITORY EFFECTS OF FULLERENE C60DERIVATIVES ON ENDOTHELIUM-DERIVED RELAXATION IN RABBIT THORACIC AORTA. ACTA ACUST UNITED AC 2001. [DOI: 10.1081/fst-100102961] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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55
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Armstead WM. NOC/oFQ PKC-dependent superoxide generation contributes to hypoxic-ischemic impairment of NMDA cerebrovasodilation. Am J Physiol Heart Circ Physiol 2000; 279:H2678-84. [PMID: 11087221 DOI: 10.1152/ajpheart.2000.279.6.h2678] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study determined whether nociceptin/orphanin FQ (NOC/oFQ) generates superoxide anion (O(2)(-)) in a protein kinase C (PKC)-dependent manner and whether such production contributes to hypoxic-ischemic (H-I) impairment of N-methyl-D-aspartate (NMDA)-induced pial artery dilation in newborn pigs equipped with closed cranial windows. Superoxide dismutase (SOD)-inhibitable nitroblue tetrazolium (NBT) reduction was an index of O(2)(-) generation. Under non-H-I conditions, topical NOC/oFQ (10(-10) M, concentration present in cerebrospinal fluid after I or H-I) increased SOD-inhibitable NBT reduction from 1 +/- 1 to 20 +/- 3 pmol/mm(2). PKC inhibitors staurosporine and chelerythrine (10(-7) M) blunted NBT reduction (1 +/- 1 to 7 +/- 2 pmol/mm(2) for chelerythrine), whereas the NOC/oFQ receptor antagonist [F/G]NOC/oFQ (1-13)-NH(2) (10(-6) M) blocked NBT reduction. [F/G]NOC/oFQ(1-13)-NH(2) and staurosporine also blunted the NBT reduction observed after I or H-I. NMDA (10(-8), 10(-6) M)-induced pial artery dilation was reversed to vasoconstriction after H-I. The NOC/oFQ antagonist staurosporine and free radical scavengers partially prevented this impaired dilation (sham: 9 +/- 1 and 16 +/- 1; H-I: -5 and -10 +/- 1; H-I staurosporine pretreated: 3 +/- 1 and 6 +/- 1%). These data show that NOC/oFQ increased O(2)(-) production in a PKC-dependent manner and contributed to this production after insult and that NOC/oFQ contributed to impaired NMDA-induced pial artery dilation after H-I, suggesting, therefore, that PKC-dependent O(2)(-) generation by NOC/oFQ links NOC/oFQ release to impaired NMDA dilation after H-I.
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Affiliation(s)
- W M Armstead
- Departments of Anesthesia and Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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56
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Gunnett CA, Heistad DD, Berg DJ, Faraci FM. IL-10 deficiency increases superoxide and endothelial dysfunction during inflammation. Am J Physiol Heart Circ Physiol 2000; 279:H1555-62. [PMID: 11009441 DOI: 10.1152/ajpheart.2000.279.4.h1555] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Little is known about the role of interleukin-10 (IL-10), an anti-inflammatory cytokine, in blood vessels. We used IL-10-deficient mice (IL-10 -/-) to examine the hypothesis that IL-10 protects endothelial function after lipopolysaccharide (LPS) treatment. The responses of carotid arteries were studied in vitro 6 h after injection of a relatively low dose of LPS (10 microgram ip). In IL-10 -/- mice, the maximum relaxation to ACh (3 microM) was 56 +/- 6% (means +/- SE) after LPS injection and 84 +/- 4% after vehicle injection (P < 0.05). Thus endothelium-dependent relaxation was impaired in carotid arteries from IL-10 -/- mice after LPS injection. In contrast, this dose of LPS did not alter relaxation to ACh in vessels from wild-type (IL-10 +/+) mice. Relaxation to nitroprusside and papaverine was similar in arteries from both IL-10 -/- and IL-10 +/+ mice after vehicle or LPS injection. Because inflammation is associated with increased levels of reactive oxygen species, we also tested the hypothesis that superoxide contributes to the impairment of endothelial function by LPS in the absence of IL-10. Results using confocal microscopy and hydroethidine indicated that levels of superoxide are elevated in carotid arteries from IL-10 -/- mice compared with IL-10 +/+ mice after LPS injection. The impaired relaxation of arteries from IL-10 -/- mice after LPS injection was restored to normal by polyethylene glycol-suspended superoxide dismutase (50 U/ml) or allopurinol (1 mM), an inhibitor of xanthine oxidase. These data provide direct evidence that IL-10 protects endothelial function after an acute inflammatory stimulus by limiting local increases in superoxide. The source of superoxide in this model may be xanthine oxidase.
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Affiliation(s)
- C A Gunnett
- Department of Internal Medicine and Department of Pharmacology, Cardiovascular Center, University of Iowa College of Medicine, Iowa City, Iowa 52242-1081, USA
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57
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ARMSTEAD WILLIAMM. Age-Dependent Cerebral Hemodynamic Effects of Traumatic Brain Injury in Newborn and Juvenile Pigs. Microcirculation 2000. [DOI: 10.1111/j.1549-8719.2000.tb00123.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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58
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Abstract
Metabolism of oxygen by cells generates potentially deleterious reactive oxygen species, including superoxide anion radical, hydrogen peroxide, and hydroxyl radical. Under normal physiologic conditions the rate and magnitude of oxidant formation is balanced by the rate of oxidant elimination. However, an imbalance between prooxidants and antioxidants results in oxidative stress, which is the pathogenic outcome of the overproduction of oxidants that overwhelms the cellular antioxidant capacity. There is increasing evidence that an elevation of oxidative stress and associated oxidative damages are mediators of vascular injury in various cardiovascular pathologies, including hypertension, atherosclerosis, and ischemia-reperfusion. This review focuses on the vascular effects of reactive oxygen species and the role of oxidative stress in vascular damage in hypertension.
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Affiliation(s)
- R M Touyz
- MRC Multidisciplinary Research Group on Hypertension, Clinical Research Institute of Montreal, 110 Pine Avenue West, Montreal, Quebec H2W 1R7, Canada.
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59
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Gupte SA, Rupawalla T, Mohazzab-H KM, Wolin MS. Regulation of NO-elicited pulmonary artery relaxation and guanylate cyclase activation by NADH oxidase and SOD. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:H1535-42. [PMID: 10330236 DOI: 10.1152/ajpheart.1999.276.5.h1535] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have previously reported that inhibition of Cu/Zn superoxide dismutase (SOD) in endothelium-removed bovine pulmonary arteries (BPA) attenuates nitrovasodilator-elicited relaxation and that a NADH oxidase linked to the redox status of cytosolic NADH is the major detectable source of superoxide (O-2) production in this tissue. In the present study, we investigated whether NADH oxidase-derived O-2 participated in inhibition of nitrovasodilator-elicited relaxation and soluble guanylate cyclase (sGC) stimulation. Lactate (10 mM) and pyruvate (10 mM) were employed to increase and decrease, respectively, NADH-dependent O-2 production in the BPA presumably by modulating cytosolic NAD(H) through the lactate dehydrogenase reaction. A 30-min pretreatment with 10 mM diethyldithiocarbamate (DETCA) was used to inhibit Cu/Zn SOD, and S-nitroso-N-acetylpenicillamine (SNAP) was employed as a source of nitric oxide (NO). Lactate or pyruvate did not alter relaxation to NO. However, when the response to NO was inhibited by DETCA, lactate potentiated and pyruvate reduced the inhibitory effects of DETCA. SOD attenuated the inhibitory effects of DETCA plus lactate. In the presence of 10 microM SNAP, the activity of sGC in a BPA homogenate preparation (which was reconcentrated to approximate tissue conditions) was not altered by SOD. However, NADH (0.1 mM) decreased sGC activity by 70%, and this effect of NADH was attenuated in the presence of SOD. Thus cytosolic NADH redox and Cu/Zn SOD activity have important roles in controlling the inhibitory effects of O-2 derived from NADH oxidase on sGC activity and cGMP-mediated relaxation to nitrovasodilators in BPA.
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Affiliation(s)
- S A Gupte
- Department of Physiology, New York Medical College, Valhalla, New York 10595, USA
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60
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Hibino M, Okumura K, Iwama Y, Mokuno S, Osanai H, Matsui H, Toki Y, Ito T. Oxygen-derived free radical-induced vasoconstriction by thromboxane A2 in aorta of the spontaneously hypertensive rat. J Cardiovasc Pharmacol 1999; 33:605-10. [PMID: 10218731 DOI: 10.1097/00005344-199904000-00013] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study was performed to clarify the mechanism of vasoconstriction induced by oxygen-derived free radicals in spontaneously hypertensive rats. The isometric tension of aortic rings from spontaneously hypertensive rats and Wistar-Kyoto rats was measured in Krebs-Henseleit solution. Oxygen-derived free radicals were generated by mixing xanthine and xanthine oxidase. The removal of endothelium enhanced the contractions induced by oxygen-derived free radicals. The inhibition of nitric oxide production with NG-nitro-L-arginine methyl ester (10(-4) M) enhanced the contractions. Treatment with the thromboxane A2 (TXA2) synthetase inhibitor OKY-046 (10(-4) M) or RS-5186 (10(-4) M) markedly reduced the contractions. Treatment with the cyclooxygenase inhibitor indomethacin (10(-5) M) and a TXA2/prostaglandin H2 (PGH2) receptor antagonist, ONO-3708 (10(-6) M), completely abolished the oxygen-derived free radical-induced contractions. In contrast, treatment with the PGI2 synthetase inhibitor tranylcypromine (10(-4) M) did not attenuate the oxygen-derived free radical-induced contractions. Whether endothelium was present or not, the release of TXB2, PGE2, and 6-keto-PGF1alpha, but not PGF2alpha, was increased by the production of oxygen-derived free radicals. Catalase and the hydroxyl radical scavenger deferoxamine plus mannitol markedly inhibited the oxygen-derived free radical-induced contractions. These results suggest that oxygen-derived free radical-induced vasoconstriction in spontaneously hypertensive rat aorta is caused by TXA2 and PGH2 released in smooth muscle.
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Affiliation(s)
- M Hibino
- Internal Medicine II, Nagoya University School of Medicine, Japan
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61
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Armstead WM. Cerebral hemodynamics after traumatic brain injury of immature brain. EXPERIMENTAL AND TOXICOLOGIC PATHOLOGY : OFFICIAL JOURNAL OF THE GESELLSCHAFT FUR TOXIKOLOGISCHE PATHOLOGIE 1999; 51:137-42. [PMID: 10192582 DOI: 10.1016/s0940-2993(99)80087-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
These studies were designed to characterize the cerebral hemodynamic effects of fluid percussion brain injury (FPI) in the newborn pig equipped with a closed cranial window. Reductions in cerebral blood flow, pial artery diameter, and cerebral oxygenation following FPI were greater in newborn (1-3 days old) vs. juvenile (3-4 weeks old) pigs, suggesting that newborns were exquisitely sensitive to brain injury. Additionally, in piglets, there was decremented dilation to nitric oxide, cGMP, and cAMP dependent stimuli following FPI. The membrane potential of vascular muscle is an important contributor to vascular tone and the activity of K+ channels is an important regulator of membrane potential. Recent studies indicate that altered dilator responsiveness and cerebral hemodynamic control following FPI results from impaired K+ ATP sensitive (KATP) and calcium sensitive (Kca+2) channel function. Impaired KATP channel function results, at least in part, from protein kinase C activation by the peptide endothelin-1. These observations indicate that the effects of brain injury on cerebral hemodynamics in the newborn are multifaceted and multifactorial.
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Affiliation(s)
- W M Armstead
- Department of Anesthesia, University of Pennsylvania and The Childrenś Hospital of Philadelphia, 19104, USA
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62
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Iadecola C, Zhang F, Niwa K, Eckman C, Turner SK, Fischer E, Younkin S, Borchelt DR, Hsiao KK, Carlson GA. SOD1 rescues cerebral endothelial dysfunction in mice overexpressing amyloid precursor protein. Nat Neurosci 1999; 2:157-61. [PMID: 10195200 DOI: 10.1038/5715] [Citation(s) in RCA: 318] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Peptides derived from proteolytic processing of the beta-amyloid precursor protein (APP), including the amyloid-beta peptide, are important for the pathogenesis of Alzheimer's dementia. We found that transgenic mice overexpressing APP have a profound and selective impairment in endothelium-dependent regulation of the neocortical microcirculation. Such endothelial dysfunction was not found in transgenic mice expressing both APP and superoxide dismutase-1 (SOD1) or in APP transgenics in which SOD was topically applied to the cerebral cortex. These cerebrovascular effects of peptides derived from APP processing may contribute to the alterations in cerebral blood flow and to neuronal dysfunction in Alzheimer's dementia.
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Affiliation(s)
- C Iadecola
- Department of Neurology, University of Minnesota, Minneapolis 55455, USA.
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63
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Mori T, Asano T, Matsui T, Muramatsu H, Ueda M, Kamiya T, Katayama Y, Abe T. Intraluminal increase of superoxide anion following transient focal cerebral ischemia in rats. Brain Res 1999; 816:350-7. [PMID: 9878822 DOI: 10.1016/s0006-8993(98)01124-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Using a modification of Karnovsky's Mn2+/diaminobenzizine (DAB) technique, we examined the production of superoxide anion (.O-2) in the vascular lumen following transient occlusion and reperfusion of the left middle cerebral artery (MCA) in Sprague-Dawley rats. The MCA was occluded for 2 h using an intraluminal suture method. Zero, 15, 30, and 60 min after reperfusion, animals were perfused transcardially with buffer containing Mn2+ and DAB, and brain samples were prepared for light and electron microscopic examination. The amber reaction deposits of.O-2 were observable to the naked eye along the major cerebral vessels of the ischemic hemisphere after each reperfusion period. Upon microscopic examination the deposits were revealed to be within arterial, capillary, and venular lumen. The amount of reaction deposits in the ischemic hemisphere corresponded to the duration of reperfusion. The formation of.O-2 was suppressed when the perfusate contained superoxide dismutase and when either Mn2+ or DAB was omitted, confirming that the reaction products produced are due to the enhanced production of.O-2. These results show that there is a progressive increase in intraluminal. O-2 during reperfusion following an ischemic insult which may participate in the aggravation of cerebral damage.
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Affiliation(s)
- T Mori
- Institute of Laboratory Animal Science, Saitama Medical Center/School, 1981 Kamoda, Kawagoe, Saitama 350-8550, Japan
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64
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Golding EM, Steenberg ML, Cherian L, Marrelli SP, Robertson CS, Bryan RM. Endothelial-mediated dilations following severe controlled cortical impact injury in the rat middle cerebral artery. J Neurotrauma 1998; 15:635-44. [PMID: 9726262 DOI: 10.1089/neu.1998.15.635] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The mechanisms associated with dysfunction of the cerebral vasculature following head trauma have not yet been fully elucidated. In an attempt to shed more light on the matter, we investigated the endothelial-mediated dilations in the rat middle cerebral artery (MCA) following severe traumatic brain injury (TBI). Rats were subjected to severe controlled cortical impact injury (CCI; 5 m/s, 130 ms duration, 3 mm deformation) over the right parietal cortex. At 24 h postinjury, ipsilateral segments of MCA and corresponding contralateral segments were isolated, mounted in a vessel chamber, and pressurized. The responses to 2 methylthio-ATP (2MeSATP), a selective agonist for the P2Y1 purinoceptors, N(omega)-nitro-L-arginine (L-NAME), an NO synthase inhibitor, and S-nitroso-N-acetylpenicillamine (SNAP), an exogenous NO donor, were determined. 2MeSATP elicited concentration dependent dilations in all MCAs studied. Ipsilateral MCAs harvested following TBI or sham-TBI, showed similar maximum dilations to 2MeSATP [70 +/- 4% (n = 17) and 72 +/- 6% (n = 13), respectively]. However, TBI reduced the concentration of 2MeSATP necessary to elicit one-half of the maximum dilation (EC50) from 15 to 9 nM (p < 0.05). Inhibition of NO synthase with 10(-5) M L-NAME abolished the dilation to 2MeSATP in both TBI and sham-TBI MCAs. The constriction to L-NAME was significantly reduced in TBI MCAs compared to sham vessels. Dilations to SNAP, an NO donor, were not altered by TBI indicating that the mechanisms of dilation involving NO in the vascular smooth muscle were not affected. Unlike other pathological conditions which often diminish endothelial-mediated responses, severe TBI enhanced the sensitivity to 2MeSATP without altering the maximum response.
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MESH Headings
- Adenosine Triphosphate/analogs & derivatives
- Analysis of Variance
- Animals
- Brain Injuries/metabolism
- Brain Injuries/physiopathology
- Cerebral Arteries/metabolism
- Cerebral Arteries/physiopathology
- Cerebrovascular Circulation/physiology
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiopathology
- Enzyme Inhibitors
- Linear Models
- Male
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiopathology
- NG-Nitroarginine Methyl Ester
- Nitric Oxide/metabolism
- Penicillamine/analogs & derivatives
- Rats
- Rats, Long-Evans
- Receptors, Purinergic P2/physiology
- Thionucleotides
- Vasodilation/drug effects
- Vasodilation/physiology
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Affiliation(s)
- E M Golding
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030, USA
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65
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Zhang F, Slungaard A, Vercellotti GM, Iadecola C. Superoxide-dependent cerebrovascular effects of homocysteine. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:R1704-11. [PMID: 9608025 DOI: 10.1152/ajpregu.1998.274.6.r1704] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recent evidence indicates that elevated plasma levels of homocysteine are a risk factor for ischemic cerebrovascular diseases. However, little is known about cerebrovascular effects of homocysteine. Homocysteine could impair cerebrovascular function by metal-catalyzed production of activated oxygen species. We studied whether homocysteine, in the presence of Cu2+, alters reactivity of cerebral circulation and, if so, whether this effect depends on O-2 generation. In halothane-anesthetized rats the parietal cortex was exposed and superfused with Ringer solution. Cerebrocortical blood flow (CBF) was monitored by a laser-Doppler probe. With Ringer solution superfusion, CBF increased with hypercapnia (+134 +/- 7%; PCO2 = 50-60 mmHg) and topical application of 10 microM ACh (+35 +/- 3%), the NO donor S-nitroso-N-acetylpenicillamine (SNAP, 500 microM; +66 +/- 6%), or 1 mM papaverine (+100 +/- 6%; n = 5). Superfusion with 40 microM Cu2+ alone did not perturb resting CBF or responses to hypercapnia, ACh, SNAP, or papaverine (P > 0.05, n = 5). However, superfusion of homocysteine-Cu2+ reduced resting CBF (-28 +/- 4%) and attenuated (P < 0.05) responses to hypercapnia (-31 +/- 9%), ACh (-73 +/- 6%), or SNAP (-48 +/- 4%), but not papaverine. The effect was observed only at 1 mM homocysteine. Cerebrovascular effects of homocysteine-Cu2+ were prevented by coadministration of superoxide dismutase (SOD; 1,000 U/ml; n = 5). SOD alone did not affect resting CBF or CBF reactivity (n = 5). The observation that homocysteine-Cu2+ attenuates the response to hypercapnia, ACh, and SNAP, but not the NO-independent vasodilator papaverine, suggests that homocysteine-Cu2+ selectively impairs NO-related cerebrovascular responses. The fact that SOD prevents such impairment indicates that the effect of homocysteine is O-2 dependent. The data support the conclusion that O-2, generated by the reaction of homocysteine with Cu2+, inhibits NO-related cerebrovascular responses by scavenging NO, perhaps through peroxynitrite formation. O-2-mediated scavenging of NO might be one of the mechanisms by which hyperhomocysteinemia predisposes to cerebrovascular diseases.
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Affiliation(s)
- F Zhang
- Laboratory of Cerebrovascular Biology and Stroke, Department of Neurology, University of Minnesota Medical School, Minnesota 55455, USA
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66
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Faraci FM, Heistad DD. Regulation of the cerebral circulation: role of endothelium and potassium channels. Physiol Rev 1998; 78:53-97. [PMID: 9457169 DOI: 10.1152/physrev.1998.78.1.53] [Citation(s) in RCA: 608] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Several new concepts have emerged in relation to mechanisms that contribute to regulation of the cerebral circulation. This review focuses on some physiological mechanisms of cerebral vasodilatation and alteration of these mechanisms by disease states. One mechanism involves release of vasoactive factors by the endothelium that affect underlying vascular muscle. These factors include endothelium-derived relaxing factor (nitric oxide), prostacyclin, and endothelium-derived hyperpolarizing factor(s). The normal vasodilator influence of endothelium is impaired by some disease states. Under pathophysiological conditions, endothelium may produce potent contracting factors such as endothelin. Another major mechanism of regulation of cerebral vascular tone relates to potassium channels. Activation of potassium channels appears to mediate relaxation of cerebral vessels to diverse stimuli including receptor-mediated agonists, intracellular second messenger, and hypoxia. Endothelial- and potassium channel-based mechanisms are related because several endothelium-derived factors produce relaxation by activation of potassium channels. The influence of potassium channels may be altered by disease states including chronic hypertension, subarachnoid hemorrhage, and diabetes.
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Affiliation(s)
- F M Faraci
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, USA
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67
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Affiliation(s)
- Julio A. Panza
- Cardiology Branch, National Heart, Lung, and Blood InstituteNational Institutes of HealthBethesdaMarylandUSA
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68
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Satoh M, Matsuo K, Kiriya H, Mashino T, Nagano T, Hirobe M, Takayanagi I. Inhibitory effects of a fullerene derivative, dimalonic acid C60, on nitric oxide-induced relaxation of rabbit aorta. Eur J Pharmacol 1997; 327:175-81. [PMID: 9200557 DOI: 10.1016/s0014-2999(97)89658-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Dimalonic acid C60 (10(-5) M), a new fullerene derivative, produced an augmentation of phenylephrine-induced tone and reduced both the acetylcholine-induced maximum relaxation and the amplitude of substance P (10(-8) M)-induced relaxation in endothelium-containing thoracic aorta of rabbit; the acetylcholine- and substance P-induced relaxation was restored in the presence of superoxide dismutase (250 U/ml). Dimalonic acid C60 (10(-5) M) did not influence the phenylephrine-induced contractile response in the absence of endothelium, but the acetylcholine-induced relaxation was eliminated by removal of the endothelium. Superoxide anion generation, using hypoxanthine (1 mM)/xanthine oxidase (16 mU/ml), reduced the acetylcholine-induced relaxation and produced an augmentation of phenylephrine-induced tone in endothelium-containing strips; these effects were negated by the addition of superoxide dismutase (250 U/ml). A nitric oxide-generating agent, S-nitroso-N-acetylpenicillamine, caused relaxation of aorta without endothelium in a concentration-dependent manner, and the concentration-response curve was shifted to the right in the presence of dimalonic acid C60. This inhibitory effect of dimalonic acid C60 was also masked in the presence of superoxide dismutase. Sodium nitroprusside-induced relaxation was not affected by either dimalonic acid C60 or superoxide dismutase. These observations suggest that dimalonic acid C60 inhibits endothelium (nitric oxide)-dependent agonist-induced relaxation through the production of superoxide.
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Affiliation(s)
- M Satoh
- Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Funabashi, Chiba, Japan.
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69
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Yu AM, Zhang HL, Chen HY. Electrocatalytic Reduction and Determination of Nitric Oxide at a Hemoglobin Modified Electrode. ANAL LETT 1997. [DOI: 10.1080/00032719708002314] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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70
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Ishimitsu T, Tobian L, Sugimoto K, Everson T. High potassium diets reduce vascular and plasma lipid peroxides in stroke-prone spontaneously hypertensive rats. Clin Exp Hypertens 1996; 18:659-73. [PMID: 8781752 DOI: 10.3109/10641969609081773] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We examined the effect of high potassium (K) diet on oxidative stress to endothelium in hypertensive rats. Five-week-old stroke-prone spontaneously hypertensive rats (SHRsp) were fed a 5% high NaCl diet containing either 0.5% normal K (n = 28) or 2.1% high K (n = 19) for 6 weeks, and lipid peroxides in the aortic intima and plasma were measured. Lipid peroxides were extracted into an organic solvent to avoid the interference of carbohydrates or glycoproteins, and malondialdehyde (MDA) produced from lipid peroxides by acid-heating was measured by its reaction to thiobarbituric acid. The antioxidant butylated hydroxytoluene prevented spurious lipid peroxide formation during the whole procedure, and optimum Fe3+ allowed a maximum MDA production from lipid peroxides. The high K SHRsp showed lower lipid peroxide levels than the normal K SHRsp both in the intima (5.6 +/- 0.3 vs. 7.2 +/- 0.4 nmol MDA/mg fatty acids, p < 0.003) and plasma (0.91 +/- 0.08 vs. 1.46 +/- 0.10 nmol MDA/ml, p < 0.001). Mean arterial pressure was slightly lower by 13 mmHg in the high K SHRsp, but these differences were still obvious even when we compared groups of rats with precisely matching blood pressures. These results indicate that high K diets reduce oxidative stress on the endothelium of high NaCl-fed SHRsp independently of blood pressure changes. This effect may be involved in the mechanism by which high K diets protect endothelium and reduce stroke incidence in hypertensive animals. Thus, we improved the method of lipid peroxide measurement and propose the protective effects of high K diet against oxidative stress to endothelium in hypertension animals.
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Affiliation(s)
- T Ishimitsu
- Department of Medicine, University of Minnesota, Minneapolis 55455, USA
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71
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Tietjen CS, Hurn PD, Ulatowski JA, Kirsch JR. Treatment modalities for hypertensive patients with intracranial pathology: options and risks. Crit Care Med 1996; 24:311-22. [PMID: 8605807 DOI: 10.1097/00003246-199602000-00022] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVES To review the cerebrovascular pathophysiology of hypertension, and the risks and benefits of antihypertensive therapies in the patient with intracranial ischemic or space-occupying pathology. DATA SOURCES Review of English language scientific and clinical literature, using MEDLINE search. STUDY SELECTION Pertinent literature is referenced, including clinical and laboratory investigations, to demonstrate principles of pathophysiology and controversies regarding the treatment of hypertension in patients with intracranial ischemic or space-occupying pathology. DATA EXTRACTION The literature was reviewed to summarize the pathophysiology, risks, and benefits of antihypertensive therapies in the patient with intracranial ischemic or space-occupying pathology. Treatment strategies were outlined with a particular emphasis on how antihypertensive agents may affect the brain. DATA SYNTHESIS Cerebral autoregulation typically occurs over a range of cerebral perfusion pressures between 50 and 150 mm Hg. Chronic hypertension results in adaptive changes that allow cerebral autoregulation to occur over a high range of pressures. Acute hypertension (rapid increase in perfusion pressure above the autoregulatory limit) may result in cerebral edema, persistent vasodilation, and brain injury. Treatment of a hypertensive emergency must be undertaken conservatively since the chronically hypertensive patient is at risk for ischemic brain injury when perfusion pressure is rapidly decreased beyond autoregulatory limits. In the patient with head injury or primary neurologic injury, acute antihypertensive intervention can result in further brain injury. Selection of appropriate antihypertensive therapy necessitates the careful consideration of agent-specific effects on cerebral blood flow, autoregulation, and intracranial pressure. For example, some vasodilators treat hypertension but also dilate the cerebral vasculature, and increase cerebral blood volume and intracranial pressure while decreasing cerebral perfusion pressure. Pharmacologic blockade of alpha 1- or beta 1-adrenergic receptors can reduce arterial blood pressure with little or no effect on intracranial pressure within the autoregulatory range. Like the direct peripheral vasodilators, calcium-channel antagonists are limited by cerebral vasodilation and increased intracranial pressure. Angiotensin converting enzyme inhibitors can also be used for mild to moderate hypertension but have the potential to further increase intracranial pressure in patients with intracranial hypertension. Barbiturates offer an alternative antihypertensive therapy since they decrease blood pressure as well as cerebral blood flow and oxygen metabolism. CONCLUSIONS The treatment of acute hypertension in the patient with intracranial ischemic or space-occupying pathology requires an understanding of the pathophysiology of hypertension and determinants of cerebral perfusion pressure. Individual agents should be selected based on their ability to promptly and reliably decrease blood pressure, while considering effects on cerebral blood flow and intracranial pressure.
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Affiliation(s)
- C S Tietjen
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, MD, USA
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72
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Pignac J, Lacaille C, Dumont L. Protective effects of the K+ ATP channel opener, aprikalim, against free radicals in isolated rabbit hearts. Free Radic Biol Med 1996; 20:383-9. [PMID: 8720909 DOI: 10.1016/0891-5849(96)02091-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Aprikalim, a K+ ATP channel opener, is a potent vasodilator with demonstrated cardioprotective properties against ischemia/reperfusion injury. It is still unknown if K+ ATP channel openers exert their beneficial effects via interaction with oxygen-derived free radicals. Therefore, we investigated the cardioprotective effects of aprikalim against oxygen-derived free radicals. Isolated rabbit hearts were perfused at constant pressure (85 cm H2O) or constant flow (30-35 ml/min). Heart rate, left ventricular developed pressure (LVDP), and either coronary flow or coronary perfusion pressure (CPP) were monitored. Free radicals were produced by electrolysis of the perfusate (0.6 mA, direct current), and 10 microM aprikalim was infused before and after exposure to free radicals. In the constant perfusion pressure experiments, 10 min of exposure to free radicals resulted in a significant reduction of heart rate (137 to 129 beats/min), LVDP (112 to 91 mmHg) and coronary flow (37 to 29 ml/min); coronary flow was more markedly impaired than contractile function. Acetylcholine-induced coronary dilation was also significantly attenuated in the presence of free radicals. After 30 min of recovery, both coronary flow and LVDP were still significantly decreased while acetylcholine-induced coronary dilation had fully recuperated. Aprikalim completely abated the coronary and cardiac depressant actions of free radicals. Constant flow experiments indicated that exposure to free radicals increased CPP (+40%, p < 0.05), an effect totally suppressed by aprikalim. These results demonstrate that aprikalim reverses the cardiodepressant actions of free radicals. The cardioprotection it afforded involves both contractile function and the coronary vasculature. Acetylcholine-induced coronary dilation was blunted by free radicals, an indication of complex interactions at the coronary endothelial level.
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Affiliation(s)
- J Pignac
- Département de Pharmacologie, Université de Montréal, Canada
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73
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DeWitt DS, Prough DS, Deal DD, Vines SM, Hoen H. Hypertonic saline does not improve cerebral oxygen delivery after head injury and mild hemorrhage in cats. Crit Care Med 1996; 24:109-17. [PMID: 8565515 DOI: 10.1097/00003246-199601000-00019] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVES To investigate the effects of hypertonic saline for resuscitation after mild hemorrhagic hypotension combined with fluid-percussion traumatic brain injury. Specifically, the effects of hypertonic saline on intracranial pressure, cerebral blood flow (radioactive microsphere method), cerebral oxygen delivery (cerebral oxygen delivery = cerebral blood flow x arterial oxygen content), and electroencephalographic activity were studied. DESIGN Randomized, controlled, intervention trial. SETTING University laboratory. SUBJECTS Thirty-four mongrel cats of either sex, anesthetized with 1.0% to 1.5% isoflurane in nitrous oxide/oxygen (70:30). INTERVENTIONS Anesthetized (isoflurane) cats were prepared for traumatic brain injury, and then randomly assigned to the following groups: moderate traumatic brain injury only (2.7 +/- 0.2 atmospheres [atm], group 1); mild hemorrhage (18 mL/kg) only, followed immediately by resuscitation with 10% hydroxyethyl starch in 0.9% saline in a volume equal to shed blood (group 2); or both traumatic brain injury (2.7 +/- 0.1 atm) and mild hemorrhage, followed immediately by replacement of a volume equal to shed blood of 10% hydroxyethyl starch in 0.9% saline (group 3); or 3.0% saline (group 4). MEASUREMENTS AND MAIN RESULTS Data were collected at baseline, at the end of hemorrhage, and at 0, 60, and 120 mins after resuscitation (or at comparable time points in group 1). Intracranial pressure in group 1 was significantly increased by traumatic brain injury at the end of hemorrhage, immediately after resuscitation, and 60 mins after resuscitation (p < .02 vs. baseline). In group 2, intracranial pressure increased significantly only immediately after resuscitation (p < .0001 vs. baseline). Groups 3 and 4 exhibited higher, although statistically insignificant, intracranial pressure increases at 60 and 120 mins after resuscitation. During resuscitation, cerebral blood flow increased significantly (p < .02 vs. baseline) in the uninjured cats. In contrast, cerebral blood flow failed to increase during resuscitation in the cats subjected to traumatic brain injury before hemorrhage and resuscitation. Although cerebral oxygen delivery in group 2 decreased significantly immediately, 60 mins, and 120 mins after resuscitation (p < .001 vs. baseline) both groups 3 and 4 had significantly lower cerebral oxygen delivery at 60 and 120 mins after resuscitation (p < .01 and p < .005, respectively, vs. group 1 at 60 mins after resuscitation, and p < .01 and p < .01, respectively, vs. group 1 at 120 mins after resuscitation). CONCLUSIONS After a combination of hemorrhage and traumatic brain injury, neither 10% hydroxyethyl starch nor 3.0% hypertonic saline restored cerebral oxygen delivery. Although neither trauma alone nor hemorrhage alone altered electroencephalographic activity, the combination produced significant decreases in electroencephalographic activity at 60 and 120 mins after resuscitation in groups 3 and 4, suggesting that cerebral oxygen delivery is inadequately restored by either resuscitation fluid. Therefore, traumatic brain injury abolished compensatory cerebral blood flow increases to hemodilution, and neither hydroxyethyl starch nor 3.0% hypertonic saline restored cerebral blood flow, cerebral oxygen delivery, or electroencephalographic activity after hemorrhagic hypotension after traumatic brain injury.
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Affiliation(s)
- D S DeWitt
- Department of Anesthesiology, University of Texas Medical Branch, Galveston 77555-0591, USA
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74
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Keaney JF, Vita JA. Atherosclerosis, oxidative stress, and antioxidant protection in endothelium-derived relaxing factor action. Prog Cardiovasc Dis 1995; 38:129-54. [PMID: 7568903 DOI: 10.1016/s0033-0620(05)80003-9] [Citation(s) in RCA: 139] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The vascular endothelium plays a central role in the regulation of vascular function. In particular, the local release of endothelium-derived relaxing factor (EDRF) regulates vascular tone and prevents platelet adhesion to the vascular wall. Impairment of EDRF action develops early in atherosclerosis and, in part, contributes to platelet deposition and vasospasm involved in the clinical expression of coronary artery disease. Recent evidence suggests that an imbalance between vascular oxidative stress and antioxidant protection is involved in the development of this vascular dysfunction. In this report, the relation between oxidative stress, atherosclerosis, and abnormal EDRF action is reviewed with particular attention to the effects of antioxidant supplementation in animal models of atherosclerosis and hypercholesterolemia.
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Affiliation(s)
- J F Keaney
- Evans Memorial Department of Medicine, Boston University Medical Center, MA, USA
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75
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Marín J, Rodríguez-Martínez MA. Nitric oxide, oxygen-derived free radicals and vascular endothelium. JOURNAL OF AUTONOMIC PHARMACOLOGY 1995; 15:279-307. [PMID: 8576275 DOI: 10.1111/j.1474-8673.1995.tb00311.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- J Marín
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma, Madrid, Spain
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76
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Abdalla S, Will JA. Potentiation of the hypoxic contraction of guinea-pig isolated pulmonary arteries by two inhibitors of superoxide dismutase. GENERAL PHARMACOLOGY 1995; 26:785-92. [PMID: 7635253 DOI: 10.1016/0306-3623(94)00245-i] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
1. Isolated proximal and distal extralobar branches of the pulmonary artery of the guinea-pig develop slow and well-sustained contractions in response to hypoxia (PO2 11-15 mm Hg) without prior stimulation with an agonist. These contractions are readily reversible by readministration of oxygen. 2. Incubation of these preparations with diethyldithiocarbamic acid (DETCA, 5 mM for 30 min), an inhibitor of superoxide dismutase, significantly increased the hypoxic contractions whether DETCA was added before the challenge with hypoxia or after the hypoxic contraction had reached a plateau. This treatment also reduced the oxygen-induced relaxation. 3. Similarly, incubation with triethylenetetramine (TETA, 5 mM for 30 min), another inhibitor of superoxide dismutase, produced larger potentiation of the hypoxic contraction in the two preparations and reduced the oxygen-induced relaxation. 4. Furthermore, addition of H2O2 (10(-5) M-3 x 10(-4) M) caused concentration-dependent relaxation of the hypoxic contraction while larger concentrations (10(-3) M and 3 x 10(-3) M) caused contraction that did not respond to readministration of oxygen. 5. These observations suggest that during hypoxic stress, the accumulation of superoxide anions may participate in the hypoxia-induced contraction and that the metabolism of these radicals into H2O2 by superoxide dismutase maintains the relaxed state during normoxia.
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Affiliation(s)
- S Abdalla
- Department of Biological Sciences, University of Jordan, Amman
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77
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Mian KB, Martin W. Differential sensitivity of basal and acetylcholine-stimulated activity of nitric oxide to destruction by superoxide anion in rat aorta. Br J Pharmacol 1995; 115:993-1000. [PMID: 7582532 PMCID: PMC1909027 DOI: 10.1111/j.1476-5381.1995.tb15909.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. In this study we compared the ability of superoxide anion to destroy the relaxant activity of basal and acetylcholine (ACh)-stimulated activity of NO in isolated rings of rat aorta. 2. Superoxide dismutase (SOD, 1-300 u ml-1) induced a concentration-dependent relaxation of phenylephrine (PE)-induced tone in endothelium-containing rings which was blocked by NG-nitro-L-arginine (L-NOARG, 30 microM), but had no effect on endothelium-denuded rings. It was likely therefore that the relaxant action of SOD resulted from protection of basally produced NO from destruction by superoxide anion, generated either within the tissue or in the oxygenated Krebs solution. 3. In contrast, a concentration of SOD (50 u ml-1) which produced almost maximal enhancement of basal NO activity, had no effect on ACh (10 nM-3 microM)-induced relaxation. 4. In the presence of catalase (3000 u ml-1) to prevent the actions of hydrogen peroxide, superoxide anion generation using hypoxanthine (HX, 0.1 mM)/xanthine oxidase (XO, 16 mu ml-1) produced an augmentation of PE-induced tone in endothelium-containing but not endothelium-denuded rings. This was likely to have resulted from removal of the tonic vasodilator action of basally-produced NO by superoxide anion, since it was blocked in tissues treated with SOD (250 u ml-1), NG-monomethyl-L-arginine (L-NMMA, 30 microM) or L-NOARG (30 microM). Pyrogallol (0.1 mM) had a similar action to HX/XO, but produced an additional augmentation of tone by an endothelium-independent mechanism. 5. In contrast to their ability to destroy almost completely the basal activity of NO, HX (0.1 mM)/XO(16 mu ml-1) and pyrogallol (0.1 mM) had no effect on ACh-induced relaxation at any concentration. An increase in the concentration of HX to 1 mM or pyrogallol to 0.3 mM did, however, lead to a profound decrease in the magnitude and time course of ACh-induced relaxation at all concentrations.6. Treatment with diethyldithiocarbamate (DETCA, 0.1 mM, 1 h) to inhibit endogenous Cu-Zn SOD,augmented PE-induced tone in endothelium-containing rings and abolished the ability of HX (0.1 mM)/XO (16 mu ml-1) and L-NMMA (30 microM) to augment tone. It was likely that DETCA had led to the destruction of basal NO activity by increasing superoxide anion levels since its actions were reversed by exogenous SOD (10-300 upsilon ml-1).7. In contrast to its ability to destroy basal activity of NO completely, DETCA (0.1 mM) produced only a slight blockade of ACh-induced relaxation. However, if these tissues were subsequently treated with concentrations of HX (0.1 mM)/XO (16 mu ml-1) or pyrogallol (0.1 mM), which had no effect by themselves on ACh-induced relaxation, a profound blockade was seen and this was reversed completely with SOD (250 u ml-1).8. The data suggest that basal activity of NO is more sensitive to inactivation by superoxide anion than ACh-stimulated activity and this probably results from differential protection by endogenous Cu-ZnSOD. It is possible therefore that endogenous SOD lowers superoxide anion levels to such an extent that only small amounts of NO, such as those produced under basal conditions, are destroyed. Following generation of superoxide anion with HX/XO or pyrogallol, or inhibition of Cu-Zn SOD with DETCA,levels of the free radical will increase such that greater amounts of NO, such as those produced following stimulation with ACh, will then be destroyed.
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Affiliation(s)
- K B Mian
- Clinical Research Initiative on Heart Failure, University of Glasgow
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78
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Girard P, Sercombe R, Sercombe C, Le Lem G, Seylaz J, Potier P. A new synthetic flavonoid protects endothelium-derived relaxing factor-induced relaxation in rabbit arteries in vitro: evidence for superoxide scavenging. Biochem Pharmacol 1995; 49:1533-9. [PMID: 7763296 DOI: 10.1016/0006-2952(94)00526-r] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A new synthetic flavone derivative, 6,7-dimethoxy-8-methyl-3',4',5-trihydroxyflavone, was studied for its capacity to protect the acetylcholine-induced relaxation of rabbit ear and cerebral arteries from inhibition by superoxide anion. This property was evaluated via two types of in vitro experiments, using rabbit ear or basilar arteries mounted in organ baths equipped for isometric tension measurement. When a high level of superoxide anion was generated by adding 3 x 10(-4) M pyrogallol to the bath, the relaxation to acetylcholine was substantially inhibited. This inhibition was significantly reversed by both superoxide dismutase (25 and/or 50 U/mL) and the flavonoid (3 x 10(-6) M and/or 10(-5) M) in both types of arteries. In the presence of the basal level of superoxide anion, the responses to acetylcholine were significantly potentiated by the flavonoid (10(-5) M) in the ear but not the basilar artery. Thus this flavonoid protects endothelium-dependent relaxation from high levels of superoxide anion possibly by scavenging superoxide anion and may have a certain therapeutic value as an agent capable of promoting natural vasodilatation.
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Affiliation(s)
- P Girard
- Institut de Chimie des Substances Naturelles, C.N.R.S. L.P., Gif sur Yvette, France
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79
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Hsu KS, Lin-Shiau SY. Antagonism by paraquat of the relaxing effects of acetylcholine and A23187 in rat thoracic aorta. Eur J Pharmacol 1995; 292:315-20. [PMID: 7796872 DOI: 10.1016/0926-6917(95)90038-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Paraquat, a widely used herbicide, has been reported to be capable of producing superoxide. In the present paper, therefore, the possibility of paraquat inhibiting endothelium-dependent relaxation, mediated by the production of nitric oxide, was tested. The relaxing effects of acetylcholine and A23187, but not that of sodium nitroprusside, in the rat thoracic aorta were found to be inhibited by paraquat in a concentration-dependent manner. In contrast, paraquat was totally inactive with regard to the aortic contractions induced by either norepinephrine or prostaglandin F2 alpha. The inhibitory action of paraquat could be antagonized by superoxide dismutase but not by catalase and indomethacin. All of these findings indicate that superoxide anions produced by paraquat in the endothelium contribute to a decrease in the relaxation response to acetylcholine and A23187 by interfering with endothelium-derived nitric oxide.
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Affiliation(s)
- K S Hsu
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei
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80
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Fraile ML, Conde MV, Sanz L, Moreno MJ, Marco EJ, López de Pablo AL. Different influence of superoxide anions and hydrogen peroxide on endothelial function of isolated cat cerebral and pulmonary arteries. GENERAL PHARMACOLOGY 1994; 25:1197-205. [PMID: 7875545 DOI: 10.1016/0306-3623(94)90138-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
1. Exogenous superoxide dismutase (SOD) or catalase did not modify isolated cat middle cerebral arterial basal tone. Catalase but not SOD reduced ACh relaxation. 2. H2O2 induced endothelium-independent relaxation which was abolished by catalase. 3. 3-Amino-1,2,4-triazole (AT) evoked endothelium-dependent contractions and diminished ACh relaxation. 4. Diethyldithio carbamic acid (DETC) induced endothelium-independent relaxation and did not modify ACh vasodilatation. 5. ACh relaxation of cat isolated pulmonary arteries was unaffected by SOD, catalase or AT, and diminished by DETC. 6. Endothelial catalase but neither SOD nor superoxide anions is involved in EDRF cerebral vasodilatation and H2O2 participates in ACh relaxation. In pulmonary arteries, only endothelial SOD activity plays a role.
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Affiliation(s)
- M L Fraile
- Departamento de Fisiología, Facultad de Medicina, Universidad Autónoma de Madrid, Spain
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81
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Tarry WC, Makhoul RG. L-arginine improves endothelium-dependent vasorelaxation and reduces intimal hyperplasia after balloon angioplasty. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1994; 14:938-43. [PMID: 8199185 DOI: 10.1161/01.atv.14.6.938] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Reductions in nitric oxide (NO) activity persist after arterial intimal injury and may be a factor in the development of intimal hyperplasia. NO inhibits in vitro platelet aggregation, leukocyte adhesion, and smooth muscle cell growth, all of which are key components in the process of intimal hyperplasia. We hypothesized that long-term supplementation with L-arginine, the precursor of NO, would increase NO production and thereby improve endothelium-dependent vasorelaxation and simultaneously reduce intimal hyperplasia. Twenty-six New Zealand White male rabbits were fed standard rabbit chow either with or without 2.25% L-arginine in their drinking water for 3 weeks. Then the animals underwent unilateral iliac artery angioplasty and were continued on their respective diets. Four weeks after angioplasty, the iliac arteries were harvested for functional and morphometric studies. The iliac arteries from several animals from each group were processed for study by electron microscopy. Maximal endothelium-dependent vasorelaxation in injured arteries was significantly greater in L-arginine-supplemented animals (mean +/- SEM, 71.8 +/- 4.1%; n = 6) than controls (51.4 +/- 4.0%, n = 7; P < .05). Furthermore, the intimal area in injured arteries was significantly reduced in L-arginine-supplemented animals (0.22 +/- 0.03 mm2, n = 5) compared with controls (0.34 +/- 0.03 mm2, n = 6; P < .05). These data suggest that L-arginine supplementation enhances NO production at sites of vascular healing and may reduce intimal hyperplasia.
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Affiliation(s)
- W C Tarry
- Department of Surgery, Medical College of Virginia, Richmond 23298
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82
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Abstract
Because of the molecular configuration, most free radicals are highly reactive and can cause cell injury. Protective mechanisms have evolved to provide defense against free-radical injury. Any time these defense systems are overwhelmed, such as during disease states, cell dysfunction may occur. In this review we discuss cellular sources as well as the significance of free radicals, oxidative stress, and antioxidants. A probable role of oxidative stress in various cardiac pathologies has been also analyzed. Although some methods for the detection of free radicals as well as oxidative stress have been cited, better methods to study the quantity as well as subcellular distribution of free radicals are needed in order to understand fully the role of free radicals in both health and disease.
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Affiliation(s)
- N Kaul
- Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Canada
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83
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Bertalanffy H, Kawase T, Toya S. In vivo effect of visible light on feline cortical microcirculation. Acta Neurochir (Wien) 1993; 121:174-80. [PMID: 8512016 DOI: 10.1007/bf01809271] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The present study was designed to test the hypothesis that prolonged illumination of the cerebral cortex, for instance during neurosurgical interventions, may affect the pial microcirculation. Experiments were performed with the closed window technique in cats. The cortical surface below the window was exposed to visible, cold light of 61,000 lumens/m2 (lux) over a period of 1 to 5 hours. Pial arterioles reacted with a slight initial dilatation to 106.8 +/- 2.6% of their resting diameter after switching to the high intensity light. Measurements of the cortical surface temperature showed an average temperature increase of 1.5 +/- 0.34 degrees C within the first 10 minutes of illumination. For assessment of pial vascular function, the responses to topical application of acetylcholine (ACh) were tested before and during the illumination period. The effect of sustained illumination on the cortical microcirculation consisted of abolition of the endothelium dependent relaxation due to ACh, and of intravascular thrombus formation, the latter, however, only in the presence of topically applied ACh. The suspected mechanism responsible for these functional alterations is light-induced generation of free oxygen radicals which are known to inactivate or destroy the endothelium-derived relaxing factor (EDRF). Further studies are recommended to elucidate the practical and clinical relevance of these findings to neurosurgical procedures.
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Affiliation(s)
- H Bertalanffy
- Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan
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84
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Abstract
By analogy to some pathologies (such as demyelinating diseases, arthritis and inflammatory processes) where the loss of cellular integrity is the starting point of tissue oxidative damage, it is proposed that some dementia types could be derived from a similar mechanism. The following oxidative events are proposed: (a) different agents could alter capillary or neuron integrity with the subsequent leakage of oxidases, proteases and transition metals from cellular compartments; (b) the persistence of the damaging agent, possible depletion of antioxidative defenses and concomitant loss of neuron function; (c) alteration of adjacent cells in the same manner; and (d) finally localized brain necrosis and progression of the dementia.
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Affiliation(s)
- E Roche
- Department de Biochimie Clinique, CMU, Genève, Switzerland
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85
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De Kimpe SJ, Van Heuven-Nolsen D, Nijkamp FP. Acetylcholine-induced relaxation in bovine isolated mesenteric arteries is suppressed by polymorphonuclear leukocytes. Br J Pharmacol 1993; 109:8-13. [PMID: 8388304 PMCID: PMC2175583 DOI: 10.1111/j.1476-5381.1993.tb13524.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
1. The endothelium plays a critical role in maintaining vascular tone via generation of potent vasoconstrictor and dilator substances. We examined the effect of bovine purified polymorphonuclear leukocytes (PMN) on the endothelium-dependent relaxation to acetylcholine in isolated mesenteric arteries. 2. In the presence of PMN (2.5 x 10(6) cells ml-1) the maximal relaxation to acetylcholine was decreased from 76.1 +/- 2.4% to 44.9 +/- 7.4% of the precontraction (P < 0.001). This effect was inhibited by superoxide dismutase and NG-mono-methyl-L-arginine, but not by catalase or indomethacin. 3. PMN were not able to influence significantly the endothelium-independent relaxation to nitroprusside. 4. Removal of PMN after preincubation and prior to precontraction and relaxation did not influence the acetylcholine-induced relaxation, indicating that no irreversible vascular damage had occurred. 5. Superoxide anion production by unstimulated PMN was less than 10% compared to phorbol myristate acetate-activated PMN, measured by chemiluminescence and reduction of ferricytochrome c. 6. We conclude that small amounts of superoxide anions produced by unstimulated PMN contribute to a decrease in relaxation to acetylcholine by interfering with endothelium-derived nitric oxide.
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Affiliation(s)
- S J De Kimpe
- Department of Pharmacology, Faculty of Pharmacy, Utrecht University, The Netherlands
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86
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Shiokawa Y, Holst JJ, Torben J, Rasmussen N, Schmidt P, Svendgaard NA. Cerebrovascular changes following administration of gammaglobulins against substance P or calcitonin gene related peptide in monkey with subarachnoid haemorrhage. Br J Neurosurg 1993; 7:507-18. [PMID: 7505591 DOI: 10.3109/02688699308995073] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cerebrovascular changes after intrathecal (ith) administration of gammaglobulins against substance P (SP) or calcitonin gene-related peptide (CGRP) were investigated before and following a simulated subarachnoid haemorrhage (SAH) in the squirrel monkey. The SAH was produced by injection of homologous blood into the interpeduncular fossa and the cisterna magna. The gammaglobulins were given both prior to the blood injections and daily in 5 days post-SAH. The effect of the gammaglobulins was examined by angiography pre-SAH and at 10 min and at 6 days post-SAH, i.e. the time points for maximal acute and late spasm in the present model. Cerebral blood flow (CBF) was measured under general anesthesia at day 6 post-SAH with an autoradiographic technique. Five of nine animals treated with CGRP antigammaglobulin died from respiratory failure. Four animals received SP antigammaglobulin and two control animals received normal globulin. SP antigammaglobulin per se had no effect on baseline arterial diameter, while CGRP antigammaglobulin significantly reduced the diameter of the arteries. SP antigammaglobulin prevented the occurrence of acute spasm and significantly reduced the degree of late spasm. Moreover, the reduction in CBF noted in the control SAH animals was significantly reduced. In contrast, CGRP antigammaglobulin treatment had no effect on the degree of spasm and did not cause any change in CBF as compared to controls. The finding that CGRP but not SP antigammaglobulin significantly reduces the arterial diameter in conjunction with our previous demonstration that a post-, but not preganglionic trigeminal lesion reduces the baseline arterial diameter, indicates that CGRP could be the transmitter involved in a peripheral axon reflex. The function of SP might be as a neurotransmitter conveying information to the brainstem. The transmitter role is supported by the effect of SP antigammaglobulin impairing SP containing neurons and, in that way, mimicking a bilateral trigeminal rhizotomy.
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Affiliation(s)
- Y Shiokawa
- Neurosurgical Department, Karolinska Hospital, Stockholm, Sweden
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87
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Abstract
Reactive oxygen metabolites affect binding of ligands to membrane receptors and also coupling of receptors to G-proteins and effector enzymes. Peroxidation of membrane lipids may lead to a lowered receptor density and also will alter the viscosity of the plasma membrane, which affects receptor coupling. Reactive oxygen species may also interact with thiol/disulfide moieties on receptor proteins or on other factors in the receptor system, which is responsible for alterations in receptor binding or coupling. Moreover, lipid peroxidation is associated with the phospholipase A2 pathway, which might indirectly affect receptor function. Moreover, oxidative stress may lead to a disturbance in cellular Ca(2+)-homeostasis. This might be related to an effect on Ca(2+)-mobilizing receptors, but there is also evidence for a decreased Ca(2+)-sequestration by ATPases. In addition, peroxidation of membrane lipids increases membrane permeability to Ca2+. Finally, reactive oxygen species interfere with actions of nitric oxide, thus affecting another pharmacological messenger system.
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Affiliation(s)
- A Van der Vliet
- Department of Pharmacochemistry, Faculty of Chemistry, Vrije Universiteit, Amsterdam, The Netherlands
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88
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Harrison DG, Kurz MA, Quillen JE, Sellke FW, Mügge A. Normal and pathophysiologic considerations of endothelial regulation of vascular tone and their relevance to nitrate therapy. Am J Cardiol 1992; 70:11B-17B. [PMID: 1529921 DOI: 10.1016/0002-9149(92)90589-q] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
During the past decade, it has become clear that the vascular endothelium critically influences vascular permeability, controls vessel growth, modulates hemostasis, and regulates vasomotion. This latter role of the endothelium is mediated by the liberation of a number of potent vasoactive compounds, including endothelium-derived relaxing factors, one of which is either nitric oxide or a compound that releases nitric oxide, vasoactive prostaglandins, hyperpolarizing factors, and a number of constricting factors. This role of the endothelium is dramatically altered by several diseases, including atherosclerosis, hypertension, and diabetes. Abnormalities of endothelial regulation of vascular tone may contribute to a number of clinical syndromes, including variant angina, unstable angina, syndrome X, and perhaps many others. In this review, several aspects of the endothelium-derived relaxing factor will be considered, including recent concepts regarding its synthesis, its chemical identity, and alterations in atherosclerosis. Finally, its action in the coronary microcirculation as contrasted to that of nitroglycerin will be considered.
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Affiliation(s)
- D G Harrison
- Department of Internal Medicine, Emory University School of Medicine, Atlanta, Georgia
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89
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Malinski T, Taha Z. Nitric oxide release from a single cell measured in situ by a porphyrinic-based microsensor. Nature 1992; 358:676-8. [PMID: 1495562 DOI: 10.1038/358676a0] [Citation(s) in RCA: 751] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nitric oxide is an important bioregulatory molecule, being responsible, for example, for activity of endothelium-derived relaxing factor (EDRF). Acute hypertension, diabetes, ischaemia and atherosclerosis are associated with abnormalities of EDRF. Nitric oxide is thought to be a retrograde messenger in the central nervous system. The technology is not yet available for rapid detection of NO released by a single cell in the presence of oxygen and/or nitrite, so the release, distribution and reactivity of endogenous NO in biological systems cannot be analysed. Here we describe a porphyrinic microsensor that we have developed and applied to monitoring NO release in a microsystem. We selectively measured in situ the NO released from a single cell with a response time of less than 10 ms. The microsensor consists of p-type semiconducting polymeric porphyrin and a cationic exchanger (Nafion) deposited on a thermally sharpened carbon fibre with a tip diameter of approximately 0.5 microns. The microsensor, which can be operated in either the amperometric or voltammetric mode, is characterized by a linear response up to 300 microM and a detection limit of 10 nM. Nitric oxide at the level of 10(-20) mols can be detected in a single cell.
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Affiliation(s)
- T Malinski
- Department of Chemistry, Oakland University, Rochester, Michigan 48309-4401
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90
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Abstract
Endothelium exerts an important influence on cerebral vascular tone through the production and release of a diverse group of vasoactive factors. Relaxing factors produced by endothelium include nitric oxide (or a nitric oxide-containing compound), a hyperpolarizing factor, and prostacyclin. Endothelium-derived contracting factors include cyclooxygenase products of arachidonic acid and endothelins. Several pathophysiological conditions are associated with increased formation of endothelium-derived contracting factors. Such endothelial dysfunction in the cerebral circulation may shift the balance of vascular tone toward constriction and may potentially contribute to the onset or maintainance of cerebral ischemia and stroke.
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Affiliation(s)
- F M Faraci
- Department of Internal Medicine, University of Iowa, College of Medicine, Iowa City 52242
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91
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Abstract
We examined the effect of fluid percussion brain injury on the responses to topical application of acetylcholine and serotonin, two vasoactive agents that have endothelium-dependent effects, in anesthetized cats equipped with cranial windows. Before brain injury, topical acetylcholine dilated both small and large arterioles. Thirty minutes after brain injury, acetylcholine constricted small arterioles, and the vasodilator response of large vessels was abolished. Subsequent application either of superoxide dismutase plus catalase to eliminate superoxide and hydrogen peroxide or of deferoxamine, an agent that scavenges iron and inhibits the production of hydroxyl radical via the Haber-Weiss reaction, restored the normal vasodilator responses to acetylcholine. Serotonin constricted both large and small arterioles before brain injury. After brain injury, small arterioles responded with a small vasodilation, and the response of large arterioles was abolished. After application of superoxide dismutase and catalase, the normal vasoconstrictor response to serotonin was restored. The results show that endothelium-dependent vasodilation from acetylcholine is eliminated by brain injury by a mechanism that involves the generation of oxygen radicals, and, more specifically, the production of hydroxyl radical. The results with serotonin are explained by the elimination by oxygen radicals of a vasoconstrictor agent generated by this agent, perhaps an endothelium-derived contracting factor.
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Affiliation(s)
- H A Kontos
- Department of Medicine, Medical College of Virginia, Richmond
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92
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Omar BA, Flores SC, McCord JM. Superoxide dismutase: pharmacological developments and applications. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1992; 23:109-61. [PMID: 1531762 DOI: 10.1016/s1054-3589(08)60964-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- B A Omar
- Webb-Waring Lung Institute, University of Colorado Health Sciences Center, Denver 80262
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93
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Wolin MS. Activated oxygen metabolites as regulators of vascular tone. KLINISCHE WOCHENSCHRIFT 1991; 69:1046-9. [PMID: 1798278 DOI: 10.1007/bf01645156] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Oxygen metabolites have been reported to produce vasoconstriction and/or vasodilation in a variety of in vitro or in vivo vascular preparations. Certain basic mechanisms appear to contribute to these responses. Hydrogen peroxide can produce either vasodilation or constriction via stimulation of prostaglandins. The soluble form of guanylate cyclase in vascular smooth muscle, an enzyme which produces the intracellular mediator of relaxation cyclic GMP, is also a site of action of vasoactive O2 metabolites. Guanylate cyclase is directly activated by nanomolar concentrations of nitric oxide (produced by endothelial cells or nitrovasodilator drugs) or H2O2 (via its metabolism by catalase). These cyclic GMP-mediated mechanisms of relaxation are inhibited by superoxide anion, produced from endogenous sources after inhibition of superoxide dismutase or produced by pharmacological agents that undergo redox cycling. In addition, O2 metabolites may modulate vascular tone via the chemical destruction of physiological contractile agents (e.g. norepinephrine) and relaxant agents (e.g. nitric oxide), and via injury to cells important for the regulation of vascular tone (e.g. endothelium). We have found in a variety of preparations that reexposure to O2 after a brief period of severe hypoxia produces vascular responses that appear to be mediated by intracellular H2O2 generation. Thus, active O2 species may contribute to vascular responses in pathophysiological situations associated with their formation (e.g. inflammation, ischemia/reperfusion, etc.) and to the physiological regulation of vascular tone produced by changes in O2 tension (e.g. reactive hyperemia, hypoxic vasoconstriction, etc).
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Affiliation(s)
- M S Wolin
- Department of Physiology, New York Medical College, Valhalla
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94
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Murphy ME, Sies H. Reversible conversion of nitroxyl anion to nitric oxide by superoxide dismutase. Proc Natl Acad Sci U S A 1991; 88:10860-4. [PMID: 1961756 PMCID: PMC53031 DOI: 10.1073/pnas.88.23.10860] [Citation(s) in RCA: 235] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Superoxide dismutase (SOD) rapidly scavenges superoxide (O2-) and also prolongs the vasorelaxant effects of nitric oxide (NO), thought to be the endothelium-derived relaxing factor. This prolongation has been ascribed to prevention of the reaction between O2- with NO. We report that SOD supports a reversible reduction of NO to NO-. When cyanamide and catalase were used to generate NO- in the presence of SOD, NO was measured by the conversion of HbO2 to MetHb. When SOD[Cu(I)] was exposed to NO anaerobically, NO- was trapped by MetHb forming nitrosylmyoglobin. When NO was generated by 3-morpholinosydnonimine hydrochloride in the presence of SOD, NO- or a similar reductant was formed, which reduced catalase compound II and promoted the formation of the catalase [Fe(III)]-NO complex. It is, therefore, conceivable that SOD may protect NO and endothelium-derived relaxing factor by a mechanism in addition to O2- scavenging and that NO- may be a physiologically important form of endothelium-derived relaxing factor.
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Affiliation(s)
- M E Murphy
- Institut für Physiologische Chemie I, Universität Düsseldorf, Federal Republic of Germany
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95
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Ellis EF, Dodson LY, Police RJ. Restoration of cerebrovascular responsiveness to hyperventilation by the oxygen radical scavenger n-acetylcysteine following experimental traumatic brain injury. J Neurosurg 1991; 75:774-9. [PMID: 1919701 DOI: 10.3171/jns.1991.75.5.0774] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Previous experiments have shown that, following experimental fluid-percussion brain injury, cyclo-oxygenase-dependent formation of oxygen radicals prevents arteriolar vasoconstriction in response to hyperventilation. The oxygen radical scavengers superoxide dismutase and catalase restore normal reactivity; however, they are not routinely available for clinical use. The present study tested whether n-acetylcysteine (Mucomyst), an agent currently available for acetaminophen toxicity, could be used as a radical scavenger to restore reactivity after brain injury. N-acetylcysteine (163 mg/kg) was given intraperitoneally prior to or 30 minutes after fluid-percussion brain injury (2.6 atm) in cats, and reactivity to hyperventilation was tested 1 hour after injury. The authors found either that pre- or postinjury administration led to normal reactivity. Additional experiments supported the hypothesis that n-acetylcysteine is an oxygen radical scavenger, since it reduced or prevented the free radical-dependent cerebral arteriolar dilation normally induced by the topical application of arachidonic acid or bradykinin. The mechanism by which n-acetylcysteine is effective in trauma may involve direct scavenging of radicals or stimulation of glutathione peroxidase activity. The results suggest that n-acetylcysteine may be useful for treatment of oxygen free radical-mediated brain injury.
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Affiliation(s)
- E F Ellis
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond
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96
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Yang ST, Mayhan WG, Faraci FM, Heistad DD. Endothelium-dependent responses of cerebral blood vessels during chronic hypertension. Hypertension 1991; 17:612-8. [PMID: 1902437 DOI: 10.1161/01.hyp.17.5.612] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Acetylcholine produces less dilatation of pial arterioles in stroke-prone spontaneously hypertensive rats (SHRSP) than in normotensive (WKY) rats. Responses of cerebral vessels to acetylcholine and bradykinin appear to involve different mechanisms. Our first goal was to determine whether responses of pial arterioles to bradykinin are impaired in SHRSP. Diameter of pial arterioles (20-60 microns) was measured using intravital microscopy in WKY rats and SHRSP (9-12 months old). Superfusion of bradykinin (3 x 10(-7) M) dilated pial arterioles by 35 +/- 6% (mean +/- SEM) in WKY rats, but only 21 +/- 3% in SHRSP (p less than 0.05 versus WKY rats). Both nitric oxide (5 x 10(-7) M) and nitroglycerin (10(-5) M) produced similar vasodilatation in WKY rats and SHRSP. Our second goal was to determine whether alteration of postreceptor mechanisms contributes to impairment of endothelium-dependent cerebral vasodilatation in SHRSP. Calcium ionophore A23187 (10(-5) M) produced more vasodilatation in WKY rats than in SHRSP (32 +/- 8% versus 9 +/- 4%, p less than 0.05). Responses to A23187 (10(-5) M) were inhibited by indomethacin (46 +/- 13% versus 15 +/- 5%, p less than 0.05) in WKY rats, whereas responses to A23187 (10(-6) M) were potentiated modestly by indomethacin (-3 +/- 2% versus 4 +/- 2%, p less than 0.05) in SHRSP.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S T Yang
- Department of Pharmacology, University of Iowa College of Medicine, Iowa City 52242
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97
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Abstract
The vascular endothelium importantly modulates many biochemical and physiologic properties of the vascular wall, including the release of potent vasoactive factors, maintenance of an anticoagulant state and modulation of vascular growth by the release of both proliferative and antiproliferative substances. Prominent among these endothelial roles is the production of a potent vasodilator or family of vasodilators termed the endothelium-derived relaxing factor, one of which has been identified to be nitric oxide or a closely related compound. Several diseases that commonly occur in patients undergoing coronary angioplasty alter many facets of endothelial function and may predispose to adverse clinical sequelae of angioplasty, including immediate thrombosis, restenosis and vascular spasm. Several features of the endothelium-derived relaxing factor, how it is altered by pathologic processes and how these considerations relate to the immediate and late postangioplasty periods are discussed.
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Affiliation(s)
- D G Harrison
- Department of Medicine, Emory University, Atlanta, Georgia 30322
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98
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Affiliation(s)
- A H Henderson
- Department of Cardiology, University of Wales College of Medicine, Cardiff
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99
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Harrison DG. Endothelial Regulation of Vasomotor Tone in Atherosclerosis. Atherosclerosis 1991. [DOI: 10.1007/978-1-4615-3754-0_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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100
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Colton C, Yao J, Grossman Y, Gilbert D. The effect of xanthine/xanthine oxidase generated reactive oxygen species on synaptic transmission. FREE RADICAL RESEARCH COMMUNICATIONS 1991; 14:385-93. [PMID: 1663906 DOI: 10.3109/10715769109093427] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effect of reactive oxygen species generated by the interaction of xanthine and xanthine oxidase on synaptic transmission was examined at the squid giant synapse and the lobster neuromuscular junction. Exposure of these synaptic regions to xanthine/xanthine oxidase produced a significant depression in evoked release, with no change in either resting membrane properties or in the action potential. Addition of catalase to the xanthine/xanthine oxidase-containing media partially blocked the synaptic depression, indicating that H2O2 contributes to the synaptic changes induced by exposure to xanthine/xanthine oxidase. H2O2 applied directly to the perfusing media also produced a decrease in synaptic efficacy. The results demonstrate that reactive oxygen species, in general, depress evoked synaptic transmission.
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Affiliation(s)
- C Colton
- Department of Physiology and Biophysics, Georgetown University School of Medicine, Washington, DC 20007
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