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Öğe The Effect of Supplementation of Grape Seed Proanthocyanidin Extract on Vascular Dysfunction in Experimental Diabetes(MARY ANN LIEBERT, INC, 2011) Okudan, Nilsel; Bariskaner, Hulagu; Gokbel, Hakki; Sahin, Ayse Saide; Belviranli, Muaz; Baysal, HaticeIncreased oxidative stress and impaired endothelium-dependent relaxation could underlie many of the vascular complications associated with diabetes. We aimed to investigate the effect of supplementation with grape seed proanthocyanidin extract (GSPE), a natural antioxidant, on vascular responses and oxidative stress in streptozotocin-induced diabetic rats. Male Sprague-Dawley rats were divided into three groups: control rats, untreated diabetic rats, and GSPE (100 mg/kg, for 6 weeks)-supplemented diabetic rats. Thoracic aorta rings of the rats were mounted in organ baths, and relaxant responses to acetylcholine (ACh), A23187, and sodium nitroprusside (SNP) were assayed in tissues precontracted with 60mM KCl. Plasma samples used for the measurement of malondialdehyde (MDA) level and superoxide dismutase (SOD) activity. The endothelium-dependent relaxations in response to ACh and A23187 were impaired, but endothelium-independent relaxation in response to SNP did not change in diabetic rats. Supplementation with GSPE significantly improved the relaxant responses to ACh and A23187. The MDA level was significantly elevated and the plasma SOD activity was decreased in diabetic rats, but supplementation with GSPE attenuated the elevated MDA levels and increased plasma SOD activity. Thus supplementation of GSPE may attenuate oxidative stress through the inhibition of lipid peroxidation and may restore endothelial function and reduce the risk of vascular disease in diabetes.Öğe The mechanisms of vasorelaxant effect of leptin on isolated rabbit aorta(WILEY, 2007) Sahin, Ayse Saide; Bariskaner, HulaguIn the present study, we analysed the effects of leptin on rabbit aorta and the mechanisms underlying these effects. Leptin (10(-12)-10(-9) M) induced concentration-dependent relaxation in intact rabbit aorta rings precontracted with phenylephrine (10(-6) M). Removal of endothelium abolished the effects of leptin. Pretreatment of rings with N-omega-nitro-L-arginine methyl ester (10(-4) M 20 min) or catalase (1200 U/mL 20 min) significantly reduced the relaxant response to leptin when compared with the control group. The incubation of brefeldin A (3.5 x 10(-5) M 90 min), indomethacin (10(-5) M 20 min), tetraethylammonium (10(-4) M 20 min), and glibenclamide (10(-5) M, 20 min) did not affect the leptin-induced vasodilation. These results suggest that leptin relaxes the rabbit aorta. The relaxation is mediated by endothelium-derived nitric oxide and hydrogen peroxide.Öğe Preconditioning with levosimendan prevents contractile dysfunction due to H2O2-induced oxidative stress in human myocardium(LIPPINCOTT WILLIAMS & WILKINS, 2007) Sahin, Ayse Saide; Goemues, Niyazi; Duman, AtesWe studied the inotropic and possible antioxidant effects of levosimendan in human atrial strips, before and after induction of oxidative stress induced by H2O2. Levosimendan (10(-9) to 10(-6) M) increased contractions induced by electrical stimulation (ES) in human atrial strips. The maximal positive inotropic effect of levosimendan was 145.6 +/- 4.6% of predrug values. H2O2 (10-6 to 10(-3) M) significantly reduced contractions induced by ES. The maximum inhibition by H2O2 on the ES induced contraction was 47.2 +/- 3.5%. Levosimendan significantly increased the isometric contractions induced by ES when compared with the values obtained in the presence of 10(-5) M H2O2 by 89.0 +/- 4.7%, 98.9 +/- 3.4%, and 111.2 +/- 3.7% at 10(-8), 10(-7), and 10(-6) M concentrations, respectively. In concentrations of 10(-7) and 10(-6) M levosimendan, the maximum responses to ES increased when compared with the values obtained in the presence of 10(-3) M H2O2 by 87.1 +/- 3.6% and 95.1 +/- 5.3%, respectively. The cumulatively applied H2O2 (10(-6)-10(-3) M) did not change the positive inotropic response to levosimendan. In conclusion, levosimendan reverses the myocardial dysfunction induced by oxidative stress in human right atrial strips. Levosimendan prevents myocardial dysfunction if administered before oxidative stress.Öğe SUPPLEMENTATION OF GRAPE SEED EXTRACT IMPROVES VASCULAR DYSFUNCTION AND REDUCES OXIDATIVE STRESS IN STREPTOZOTOCIN-INDUCED DIABETIC RATS(SPRINGER TOKYO, 2009) Okudan, Nilsel; Bariskaner, Hulagu; Gokbel, Hakki; Sahin, Ayse Saide; Belviranli, Muaz; Baysal, Hatice[Abstract not Available]
