Real-time analysis of peritoneal function from Nitric Oxide (NO) and Reactive Oxygen Species (ROS)

一氧化氮（NO）在调节血管张力和控制局部和全身血流动力学方面起关键作用。四氢生物蝶呤（Tetrahydrobiopterin，BH_4）是维持一氧化氮合酶（nitricoxidesynthase，NOS）活性的重要辅助因子。BH_4水平的降低可能导致内皮细胞NOS解偶联，导致NO合成减少，NOS释放超氧化物增加。本研究的目的是测定CAPD患者透析液流出液中NO、BH_4和BH_2（BH_4的氧化形式）的浓度。18例慢性肾功能衰竭患者在我院接受腹膜透析参与了这项研究。我们使用NO传感器（amiNO-700，Innovative Instruments，Inc.，USA）。用HPLC测定BH_4和BH_2的浓度。4小时CAPD后透析液中的NO浓度显著高于CAPD溶液交换后立即透析液中的NO浓度（8.3±3.2 nM对3.3±0.9 nM; p<0.05）。BH_4浓度在CAPD后4小时也高于溶液交换后即刻（4.10±4.18 ng/ml vs.0.29 ±0.85 ng/ml; p<0.05）。BH 2浓度也显示出相同的趋势（0.18±0.24 ng/ml对0.07±0.10 ng/ml; p<0.05）。在CAPD治疗过程中，NO和BH_4浓度均随时间而升高。提示CAPD治疗可增加BH_4的利用率，从而提高NO的生物利用度。

Nitric oxide (NO) plays a key role in the regulation of vascular tone and controls both local and systemic hemodynamics. Also, dysfunction of the peritoneal membrane has been suggested to be related to abnormal production and/or metabolism of endogenous NO. Tetrahydrobiopterin (BH_4) is a key cofactor to maintain the enzymatic activity of nitric oxide synthase (NOS). A decrease in BH_4 level may cause endothelial NOS uncoupling, resulting in reduced NO synthesis and enhanced superoxide release from NOS. The aim of the present study was thus to measure NO, BH_4 and BH_2 (an oxidized form of BH_4) concentrations in the dialysate effluent of CAPD patients. Eighteen patients with chronic renal failure undergoing peritoneal dialysis at our hospital participated in this study. We directly measured the concentration of NO in the CAPD dialysate using an NO sensor (amiNO-700, Innovative Instruments, Inc., USA). Both BH_4 and BH_2 concentrations were measured using HPLC. NO concentration was significantly higher in the dialysate after 4 hrs CAPD than in the dialysate immediately after an exchange of CAPD solution (8.3±3.2 nM vs. 3.3±0.9 nM; p<0.05). BH_4 concentration was also higher after a 4-hr CAPD than immediately after solution exchange (4.10±4.18 ng/ml vs. 0.29±0.85 ng/ml; p<0.05). BH2 concentration also showed the same trend (0.18±0.24 ng/ml vs. 0.07±0.10 ng/ml; p<0.05). In the CAPD therapy, both NO and BH_4 concentrations increased in the course of time. These results suggest that the bioavailability of peritoneum-derived NO is increased by CAPD therapy due to the increased BH_4 availability.