The vasoactive effects of oxidative stress induced by hydrogen peroxide (H2O2) on human umbilical artery strips as well as the possible mechanisms involved are studied. Contraction responses to cumulative H2O2 (10–7 ...The vasoactive effects of oxidative stress induced by hydrogen peroxide (H2O2) on human umbilical artery strips as well as the possible mechanisms involved are studied. Contraction responses to cumulative H2O2 (10–7 M-3 × 10–2 M) in endothelium intact and denuded umbilical arteries and responses to cumulative H2O2 after incubation with L-NAME (10–4 M) (n = 8), indomethacin (10–5 M) (n = 8) and verapamil (10–6) (n = 8) were recorded. Responses elicited with cumulative H2O2 in Ca2+ free extracellular medium and the responses to cumulative Ca2+ (10–4 M-2 × 10–3 M) after H2O2 (10–3 M) induced contraction were also studied. The Emax for each experiment was calculated. p 2O2 elicited contraction was greater in endothelium denuded artery strips compared to endothelium intact strips (p 2O2 (p 2+ free extracellular medium caused decreases in cumulative H2O2 elicited contractions and cumulative Ca2+ caused concentration dependent increases in the contraction caused by a single bolus of H2O2 (p 2O2 causes concentration-dependent constriction in human umbilical arteries. The presence of the endothelium and NOS enzyme activation influences the H2O2 responses. Removal of the endothelium increases the H2O2 elicited contractions more than incubation with L-NAME suggesting beside NO, other endothelial vasodilators are also involved in vascular tonus of the umbilical arteries. Both intracellular and extracellular Ca2+ ions and constrictor cyclooxygenase metabolites play a role in the contractile responses elicited by H2O2 in human umbilical arteries.展开更多
This in vitro study was designed to assess the effects of fentanyl on isolated rabbit thoracic aorta rings contracted with phenylephrine. Methods included contraction of aorta rings with phenylephrine (10–5 M) and re...This in vitro study was designed to assess the effects of fentanyl on isolated rabbit thoracic aorta rings contracted with phenylephrine. Methods included contraction of aorta rings with phenylephrine (10–5 M) and recording the changes after increasing concentrations of fentanyl (10–9 M – 10–5 M). Similar experiments were done after incubation with Nω- nitro-L-arginine methyl ester (10–4 M), indomethacin (10-5 M), naloxone (10–5 M), ouabain (10–5 M), TEA (10–4 M) and glibenclamide (10–5 M). It was revealed that, fentanyl causes relaxation in rabbit aorta rings precontracted with phenylephrine. Removal of endothelium significantly reduces the relaxant response to fentanyl. Nitric oxide synthase inhibitor L-NAME, K+ channel blocker glibenclamide and Na+/K+ ATPase inhibitor ouabain inhibits the relaxant effect of fentanyl in endothelium intact aorta rings. These results suggest that fentanyl causes dose dependent vasodilatation in the rabbit aorta via activation of KATP channels and Na+-K+ -ATPase, and nitric oxide released from endothelium.展开更多
Aim: Increased oxidative stress plays important roles in vascular dysfunction in patients undergoing coronary artery bypass graft surgery. Hydrogen peroxide (H2O2) is used as an experimental model for oxidative stress...Aim: Increased oxidative stress plays important roles in vascular dysfunction in patients undergoing coronary artery bypass graft surgery. Hydrogen peroxide (H2O2) is used as an experimental model for oxidative stress. The present study was designed to assess the effects of levosimendan pretreatment on the contractile effects induced by H2O2 in human saphenous vein (HSV) segments. Methods: We studied H2O2 induced contractions of isolated HSV mounted in standard tissue baths. H2O2 (10-6 – 10-3 M) was added cumulatively to the organ bath. Concentration-response curves to H2O2 were repeated in the presence of levosimendan (10–8 M). In the second series of experiments, strips were contracted with 5-HT (10–5 M). When the contraction reached a stable plateau, H2O2 was administrated cumulatively into the organ bath. The same procedure was conducted in the presence of levosimendan. Results: Pretreatment of the SV strips with levosimendan significantly reduced the contractile response to each concentration of H2O2 . 5-HT produced contractions in SV strips. Further treatment of these strips with H2O2 resulted in statistically significant concentration-dependent increases in tension. Preincubation of the tissues with levosimendan did not significantly influence the maximum amplitude of the 5-HT-induced tone but inhibited the contractile effect of H2O2 on the 5-HT-induced contraction. Conclusion: Pretreatment of HSV with clinical concentrations of levosimendan inhibits the vasoconstriction caused by oxidative stress, indicating its potential preventive effect against oxidative stress induced graft spasm.展开更多
文摘The vasoactive effects of oxidative stress induced by hydrogen peroxide (H2O2) on human umbilical artery strips as well as the possible mechanisms involved are studied. Contraction responses to cumulative H2O2 (10–7 M-3 × 10–2 M) in endothelium intact and denuded umbilical arteries and responses to cumulative H2O2 after incubation with L-NAME (10–4 M) (n = 8), indomethacin (10–5 M) (n = 8) and verapamil (10–6) (n = 8) were recorded. Responses elicited with cumulative H2O2 in Ca2+ free extracellular medium and the responses to cumulative Ca2+ (10–4 M-2 × 10–3 M) after H2O2 (10–3 M) induced contraction were also studied. The Emax for each experiment was calculated. p 2O2 elicited contraction was greater in endothelium denuded artery strips compared to endothelium intact strips (p 2O2 (p 2+ free extracellular medium caused decreases in cumulative H2O2 elicited contractions and cumulative Ca2+ caused concentration dependent increases in the contraction caused by a single bolus of H2O2 (p 2O2 causes concentration-dependent constriction in human umbilical arteries. The presence of the endothelium and NOS enzyme activation influences the H2O2 responses. Removal of the endothelium increases the H2O2 elicited contractions more than incubation with L-NAME suggesting beside NO, other endothelial vasodilators are also involved in vascular tonus of the umbilical arteries. Both intracellular and extracellular Ca2+ ions and constrictor cyclooxygenase metabolites play a role in the contractile responses elicited by H2O2 in human umbilical arteries.
文摘This in vitro study was designed to assess the effects of fentanyl on isolated rabbit thoracic aorta rings contracted with phenylephrine. Methods included contraction of aorta rings with phenylephrine (10–5 M) and recording the changes after increasing concentrations of fentanyl (10–9 M – 10–5 M). Similar experiments were done after incubation with Nω- nitro-L-arginine methyl ester (10–4 M), indomethacin (10-5 M), naloxone (10–5 M), ouabain (10–5 M), TEA (10–4 M) and glibenclamide (10–5 M). It was revealed that, fentanyl causes relaxation in rabbit aorta rings precontracted with phenylephrine. Removal of endothelium significantly reduces the relaxant response to fentanyl. Nitric oxide synthase inhibitor L-NAME, K+ channel blocker glibenclamide and Na+/K+ ATPase inhibitor ouabain inhibits the relaxant effect of fentanyl in endothelium intact aorta rings. These results suggest that fentanyl causes dose dependent vasodilatation in the rabbit aorta via activation of KATP channels and Na+-K+ -ATPase, and nitric oxide released from endothelium.
文摘Aim: Increased oxidative stress plays important roles in vascular dysfunction in patients undergoing coronary artery bypass graft surgery. Hydrogen peroxide (H2O2) is used as an experimental model for oxidative stress. The present study was designed to assess the effects of levosimendan pretreatment on the contractile effects induced by H2O2 in human saphenous vein (HSV) segments. Methods: We studied H2O2 induced contractions of isolated HSV mounted in standard tissue baths. H2O2 (10-6 – 10-3 M) was added cumulatively to the organ bath. Concentration-response curves to H2O2 were repeated in the presence of levosimendan (10–8 M). In the second series of experiments, strips were contracted with 5-HT (10–5 M). When the contraction reached a stable plateau, H2O2 was administrated cumulatively into the organ bath. The same procedure was conducted in the presence of levosimendan. Results: Pretreatment of the SV strips with levosimendan significantly reduced the contractile response to each concentration of H2O2 . 5-HT produced contractions in SV strips. Further treatment of these strips with H2O2 resulted in statistically significant concentration-dependent increases in tension. Preincubation of the tissues with levosimendan did not significantly influence the maximum amplitude of the 5-HT-induced tone but inhibited the contractile effect of H2O2 on the 5-HT-induced contraction. Conclusion: Pretreatment of HSV with clinical concentrations of levosimendan inhibits the vasoconstriction caused by oxidative stress, indicating its potential preventive effect against oxidative stress induced graft spasm.
