Effects of Ginkgo biloba extract on the expression of eNOS and the release of NO in mesenteric arterioles of senile rats

Abstract

To investigate the effects of Ginkgo biloba extract (GBE) on the expression of endothelial nitric oxide synthase (eNOS) and the release of nitric oxide (NO) in mesenteric arterioles of aging rats. (1) Cytologic experiment:human umbilical vein endothelial cells (HUVEC) were randomly divided into 3 groups: control group, NG-nitro-L-arginine methyl ester (L-NAME) group and GBE group. L-NAME group: 100 µmol/L L-NAME was added into HUNEC for a 48-hour incubation. GBE group: After HUVEC was exposed to 100 µmol/L L-NAME for 24 hours, 20 g/L GBE was added for another 24-hour co-incubation. Then the expression of eNOS protein was observed in each group. (2) Animal experiment: Thirty-two 24-month-old male SD rats were randomly divided into normal control group (n = 8) and GBE group (n = 24). The GBE group was further divided into 3 groups receiving an orally dosed GBE for 3, 5, 7 days respectively. Afterward the diameter of first-order mesenteric arteriole was measured under the pressures of 20, 40, 60, 80, 100, 120, 140 mm Hg (1 mm Hg = 0.133 kPa) and the elasticity of blood vessels calculated. The release of NO, the expression of eNOS protein and its mRNA in mesenteric arterioles stimulated by the same shear stress (15 dyn/cm(2)) were evaluated respectively. (1) Cytological studies indicated that the expression of eNOS protein of the L-NAME group was significantly lower than those of the control and GBE groups (0.57 ± 0.06 vs 0.96 ± 0.05, 0.81 ± 0.09, both P < 0.01). (2) After the dosing of GBE for 3, 5, 7 days, the release of NO was significantly higher than that of the control group [(8.01 ± 0.24, 12.11 ± 0.78, 14.72 ± 0.70 vs 5.83 ± 0.75) pmol×mm(-2)×min(-1), all P < 0.05]; the expressions of eNOS protein were significantly higher than those of the control group (0.59 ± 0.20, 0.86 ± 0.02, 1.09 ± 0.13 vs 0.41 ± 0.16, all P < 0.05). And GBE was highest at Day 7; the expression levels of eNOS mRNA were significantly higher than those of the control group (0.79 ± 0.04, 0.85 ± 0.07, 0.99 ± 0.03 vs 0.58 ± 0.05, all P < 0.05). And GBE was also highest at Day 7. GBE can improve vascular flexibility through increasing the expression of eNOS and the release of NO, protecting the functions of blood vessels.