Tan Jian-xin, Huang Xiu-lan, Wang Bo, Fang Xing, Huang Di-nan
Department of Pediatrics, the Affiliated Hospital of Guangdong Medical College, Zhanjiang 524023, China.
Zhonghua Er Ke Za Zhi. 2012 Oct;50(10):782-7.
Recent studies showed that adenosine played important roles in vasodilation. This study aimed to investigate the effects of adenosine, its A1 and A2b receptor agonists on pulmonary artery hypertension (PAH) induced by chronic hypoxia in rats by continuously subcutaneous administration with an osmotic pump for 14 days, and to see if rennin angiotensin system and inducible nitric oxygen synthase (iNOS)/nitric oxide (NO) mediate the effects.
Fifty-six male SD rats were randomly assigned to seven groups. Each group included eight rats. They were normoxic group, hypoxic group, adenosine-treated group [adenosine was administered at a dose of 150 µg(kg·min) under the hypoxic condition], adenosine A1 receptor agonist CPA-treated group [CPA was administered at a dose of 20 µg/(kg·min) under the hypoxic condition], CPA plus selective adenosine A1 antagonist DPCPX-treated group [CPA and DPCPX were administered simultaneously under the hypoxic condition, the dose of CPA was the same as the above, and the dose of DPCPX was 25 µg/(kg·min)], adenosine A2b receptor agonist NECA-treated group [NECA was administered at a dose of 30 µg/(kg·min) under the hypoxic condition], NECA plus selective adenosine A2b receptor antagonist MRS-treated group[ NECA and MRS1754 were administered simultaneously under the hypoxic condition, the dose of NECA was the same as the above, and the dose of MRS1754 was 50 µg/(kg·min)]. Osmotic pumps containing adenosine or selective adenosine A1 receptor agonist (CPA), or nonselective but potent adenosine A2b receptor agonist (NECA) were placed subcutaneously 7 days after hypoxia and continuously administered the agents for 14 days.Mean pulmonary artery pressure (mPAP) was detected after administration of the agents. Then blood samples were taken from heart for measurement of renin activity, angiotensin II (AngII) and endothelin-1 (ET-1) concentration by radioimmunoassay, NO by measuring nitrate. Small pulmonary arteries were prepared for immunoreactivity staining of proliferating cell nuclear antigen (PCNA) and iNOS.
(1) Chronic hypoxia induced PAH [mPAP: (31.38 ± 3.42) mm Hg]. Adenosine or CPA or NECA administered for 14 days by subcutaneous route attenuated the mPAP [(21.17 ± 3.56) mm Hg, (22.88 ± 2.95) mm Hg, (19.81 ± 2.39) mm Hg, respectively], which showed significant difference when compared with hypoxia group (P < 0.05 respectively). (2) Plasma rennin activity and AngII level in hypoxia group [(2.51 ± 0.25) ng/(ml·h), (83.01 ± 9.38) pg/ml] were significantly higher than that in normoxic group (P < 0.05, respectively).(3) Adenosine treatment decreased the rennin activity and AngII level when compared with hypoxic group(P < 0.05, respectively);CPA and NECA attenuated respectively the rennin activity and AngII level of rats induced by chronic hypoxia (P < 0.05, respectively). (4) Adenosine administration for 14 days attenuated the wall thickness induced by chronic hypoxia (P < 0.05). CPA showed no effect on wall thickness, but NECA significantly attenuated the wall thickness (P < 0.05). (5) The number of iNOS staining positive cells in small pulmonary artery was higher in hypoxia group than in that in normoxic rats (23.75 ± 7.91 vs. 8.00 ± 2.20, P < 0.05). Adenosine or CPA, or NECA administration increased respectively the iNOS expression in rats treated with chronic hypoxia. Chronic hypoxia caused significant decrease of nitric oxide level. Adenosine treatment increased the nitric oxide level in rats treated with chronic hypoxia. CPA and NECA also increased respectively the nitric oxide level in rats treated with chronic hypoxia. Chronic hypoxia caused significant increase of ET-1 level. The ET-1 level in rats treated with adenosine, CPA or NCEA respectively were lower than that in chronic hypoxia rats (P < 0.05). (6) Adenosine treatment partially attenuated the number of PCNA-positively stained cells. NECA treatment also attenuated the PCNA expression, but CPA showed no effect.
Adenosine and its agonists CPA, NECA administered continually by subcutaneous route attenuate mPAP of rats induced by chronic hypoxia. CPA attenuates mPAP through reduction of RA/AngII activity and balance of NO/ET-1 level. NECA attenuates mPAP by inhibiting PCNA expression and proliferation of mooth muscle of pulmonary artery.
近期研究表明，腺苷在血管舒张中发挥重要作用。本研究旨在通过持续皮下注射渗透泵14天，研究腺苷及其A1和A2b受体激动剂对大鼠慢性低氧诱导的肺动脉高压（PAH）的影响，并观察肾素血管紧张素系统和诱导型一氧化氮合酶（iNOS）/一氧化氮（NO）是否介导这些作用。
56只雄性SD大鼠随机分为7组，每组8只。分别为常氧组、低氧组、腺苷治疗组[在低氧条件下以150μg/(kg·min)的剂量给予腺苷]、腺苷A1受体激动剂CPA治疗组[在低氧条件下以20μg/(kg·min)的剂量给予CPA]、CPA加选择性腺苷A1拮抗剂DPCPX治疗组[在低氧条件下同时给予CPA和DPCPX，CPA剂量同上，DPCPX剂量为25μg/(kg·min)]、腺苷A2b受体激动剂NECA治疗组[在低氧条件下以30μg/(kg·min)的剂量给予NECA]、NECA加选择性腺苷A2b受体拮抗剂MRS治疗组[在低氧条件下同时给予NECA和MRS1754，NECA剂量同上，MRS1754剂量为50μg/(kg·min)]。低氧7天后皮下植入含腺苷或选择性腺苷A1受体激动剂（CPA）或非选择性但强效的腺苷A2b受体激动剂（NECA）的渗透泵，并持续给药14天。给药后检测平均肺动脉压（mPAP）。然后从心脏取血，采用放射免疫法测定肾素活性、血管紧张素II（AngII）和内皮素-1（ET-1）浓度，通过测量硝酸盐含量测定NO。制备小肺动脉进行增殖细胞核抗原（PCNA）和iNOS的免疫反应性染色。
（1）慢性低氧诱导PAH [mPAP：(31.38±3.42)mmHg]。皮下途径给予腺苷、CPA或NECA 14天可减轻mPAP [分别为(21.17±3.56)mmHg、(22.88±2.95)mmHg、(19.81±2.39)mmHg]，与低氧组相比差异有统计学意义（P均<0.05）。（2）低氧组血浆肾素活性和AngII水平[(2.51±0.25)ng/(ml·h)、(83.01±9.38)pg/ml]显著高于常氧组（P均<0.05）。（3）与低氧组相比，腺苷治疗降低了肾素活性和AngII水平（P均<0.05）；CPA和NECA分别减轻了慢性低氧诱导的大鼠肾素活性和AngII水平（P均<0.05）。（4）腺苷给药14天减轻了慢性低氧诱导的血管壁厚度（P<0.05）。CPA对血管壁厚度无影响，但NECA显著减轻了血管壁厚度（P<0.05）。（5）低氧组小肺动脉中iNOS染色阳性细胞数高于常氧大鼠（23.75±7.91对8.00±2.20，P<0.05）。腺苷、CPA或NECA给药分别增加了慢性低氧处理大鼠的iNOS表达。慢性低氧导致一氧化氮水平显著降低。腺苷治疗增加了慢性低氧处理大鼠的一氧化氮水平。CPA和NECA也分别增加了慢性低氧处理大鼠的一氧化氮水平。慢性低氧导致ET-1水平显著升高。腺苷、CPA或NCEA处理的大鼠ET-1水平分别低于慢性低氧大鼠（P<0.05）。（6）腺苷治疗部分减轻了PCNA阳性染色细胞数。NECA治疗也减轻了PCNA表达，但CPA无影响。
皮下持续给予腺苷及其激动剂CPA、NECA可减轻慢性低氧诱导的大鼠mPAP。CPA通过降低RA/AngII活性和平衡NO/ET-1水平减轻mPAP。NECA通过抑制PCNA表达和肺动脉平滑肌增殖减轻mPAP。
