【作者】 杨鹰；

【导师】 乔健；

【作者基本信息】 中国农业大学 ， 基础兽医学， 2003， 博士

【摘要】 尽管对于哺乳动物已经确切证明内皮素是以自分泌和旁分泌的方式作用于靶细胞膜上的受体，对动物基础血压和一些疾病的发病过程有重要病理生理意义，但对于禽类，无论是内皮素的生理还是病理作用，都研究甚少。通过这个研究，首次证明内皮素-1有维持鸡体循环和肺循环基本血压的作用，并参与了低温诱发肉鸡腹水肺动脉高压综合征的发病过程。 第一部分 内皮素-1对鸡血流动力学的影响 1．用外源性ET-1注射于正常蛋鸡和肉鸡翼静脉，观察到PACP、PASP、FACP、FASP、RVSP、RVDP升高并随时间变化的曲线具有双相性和双向性，呈先降后升的趋势，也观察到RV+dp/dt和HR下降，而且ET-1对这些检测指标的影响都呈剂量依赖性，即ET-1浓度越高，指标的变化越大；对于本试验选取的蛋鸡和肉鸡，ET-1对股动脉压的影响比肺动脉压大，ET-1对蛋鸡和肉鸡同一指标的作用没有明显差异。通过这个试验证明了外源性ET-1能够改变家禽体循环和肺循环的生理平衡，主要表现为升高血压。 2．本研究证明翼静脉注射ET-1 Ab可以降低肺动脉压、股动脉压、右心室内压和心率，提示ET-1有维持家禽基本血压的作用，因ET-1 Ab与体内ET-1结合，使ET-1不能到达受体，从而降低ET-1的血管收缩作用。试验中发现抗体对于不同系统的血压作用不同，对体循环的影响比肺循环大；对肉鸡血流动力学的影响比对蛋鸡大，提示蛋鸡和肉鸡血液中ET-1的游离与结合状态比值不同。本试验结果说明，在维持家禽正常肺动脉血压的过程中，ET-1是保证肺血管张力的基本条件之一，所以，若改变和/或阻断ET-1生物学作用，就能改变家禽血流动力学。 3．用ET_AR特异性受体拮抗剂BQ123注射于正常蛋鸡和肉鸡翼静脉，也观察到可以降低肺动脉压、股动脉压、右心室内压和心率，使心肌收缩速率变大，而且BQ123对这些检测指标的影响均呈剂量依赖性，即BQ123浓度越高，指标变化越大。BQ123与ET_AR特异性结合，竞争性的阻断ET-1与ET_AR结合，使受体后信息通路不能被启动，因而使血管平滑肌和心肌紧张度下降，结果血压和心室内压下降。通过这个试验可以反证ET-1参与了家禽基本血压的生理调节。 第二部分 内皮素-1在肉鸡肺动脉高压综合征发病机制中的作用 4．常温肉鸡和低温诱发的肺动脉高压肉鸡翼静脉注射相同浓度的ET-1，发现低温肉鸡在出现PH后，ET-1仍然可以引起肺循环和体循环的血流动力学发生改变，即使肺动脉压和股动脉压都升高，但升高的幅度比常温肉鸡低，说明肺血管和心脏闲置的ET_AR发生改变(减少)，外源性ET-1与减少了的ET_AR结合，对肺动脉和股动脉的升压作用就会明显低于正常肉鸡，即PH肉鸡循环对ET-1的反应性下降。这个试验初步说明肉鸡发生肺动脉高压时，有ET-1的参与。 5．通过注射ET-1 Ab观察到肺动脉高压肉鸡肺动脉压变化比常温肉鸡大，而股动脉压没有明显变化，说明PH时，肺循环ET-1含量增加，体循环没有明显改变，提示低温诱发肉鸡PH时， 中国农业大学博士学位论文 一 ET－且的增加只在部分器官，血浆中ETI的浓度不能完全代表血管内 ETI的变化，而通过ETI Ah 与ET中和，可以间接反映PH时机体ET－l变化的特点。这个试验也证明ET－1参与了肉鸡肺 动脉高压综合征的发病过程。 6．用BQ123观察到低温诱发的肺动脉高压肉鸡股动脉压和肺动脉压都比正常肉鸡下降显著， 提示肺动脉高压肉鸡心脏和肺血管等某些器官组织发生 ETAR数量和密度的改变，而当 BQ123 与ETI竞争性的和ETAR结合后，逆转了ET－l的血管和心脏收缩作用，用受体抑制方法间接证 明了肺动脉高压时ET－l在肉鸡肺动脉高压发病机制中占有重要地位。 7．通过定时定量于低温肉鸡腹腔内注射BQ123，检测PACP、PASP、FACP、FASP、RVSP、 RVDP、RVtdpldt、HR、PCV和AHI这些指标，结果表明ETAR特异性受体桔抗剂BQ123能够 预防低温诱发肉鸡肺动脉高压，保护肺动脉和右心正常的生理功能。因为BQ123是通过桔抗ET－1 的作用起到预防和保护作用的，所以本试验结果又一次用反证法，验证了ET－l参与了肉鸡腹水 肺动脉高压的发病过程，而且为肉鸡肺动脉高压综合征提供了新的治疗途径。 本试验从宏观角度，用外源性注射ETI、受体抑制和受体前抑制三种方式直接证明正常生理 条件下，ET－l—ETAR有维持家禽基本血压的作用，还发现ETN受体桔抗剂BQ123可以预防低 温诱发的肉鸡肺动脉高压，为进一步研究ET－ETR系统在家禽某些病理生理机制中的作用提供理 论依据。更多还原

【Abstract】 There is not much information about the effects of endothelin-1 (ET-1), a potent endogenous constrictor of vascular, on haemodynamics or which ET receptor subtypes mediate ET-1-induced vasoconstrictive action in the poultry. ET-1 not only causes a potent and prolonged vasoconstriction but also are known to enhance cell proliferation and to stimulate extracellular matrix accumulation in vivo and in vitro. To clarify the actions of ET-1 underlying pulmonary circulation and systemic circulation in poultry, we investigated the effect of ET-1, BQ123 (a selective ETA receptor antagonist) and ET-1 antibody (ET-1 Ab) on the pulmonary arterial contract pressure (PACP), pulmonary arterial stretch pressure (PASP), femoral arterial contract pressure (FACP), femoral arterial stretch pressure (FASP), right ventricular systolic pressure (RVSP), the maximum increasing rate of right ventricular (RV+dp/dt), heart rate (HR) in normal laying-egg chickens, broilers with and without pulmonary hypertension (PH). We also studied the effects of long-term BQ-123 treatment on the broilers exposed to low ambient temperatures.1. ET-1 produced dose-dependent increases in PACP, PASP, FACP, FASP, RVSP, RVDP, which were rapidly decreases in onset preceded sustained biphasic ascending (first phase peaking at 1-2 minutes; second phase peaking at 10-15 minutes) after injecting 1.0 and 2.0 ug/kg ET-1 through wing veins, whereas, decreases of RV+dp/dt and HR were observed. No distinctness was found between the laying-egg chickens and broilers and there are more change in pulmonary than systemic circulation in either bird.2. ET-1 Ab (1:2500) (i.v) caused descending in PACP, PASP, FACP, FASP, RVSP, and a little ascending in RV+dp/dt and HR. The results revealed that pulmonary vessels are more sensitive to ET-1-induced vasoconstriction than systemic vessels and showed endogenous ET-1 is responsible for the basic balance of blood pressure in chicks.3. 2.0 ug/kg BQ123 (i.v.) induced PACP, PASP, FACP, FASP, RVSP increase and RV+dp/dt, HR decrease more significantly than 0.4 ug/kg BQ123, whereas, there was no evident change in saline control. These results suggest that ET-1 ?ETAR play an important role in the regulation of in systemic and pulmonary circulations.4. That much fewer increases in PACP, PASP, FACP, FASP were caused by 2.0 ug/kg ET-1 (i.v.) in broilers with PH induced by low ambient temperatures than normal broilers indicates there is some change of ET-1 in the development of PH in broilers.5. That ET-1 Ab (1:2500) induced more decreases of PACP, PASP in broiler with pulmonary hypertension induced by low ambient temperatures than the normal ones but not FACP, FASP suggestsET-1 take part in the development of PH in broilers.6. The much more decreases of PACP, PASP, FACP, FASP induced by BQ123 (2.0 ng/kg, i.v;) in PH broilers than normal broilers also demonstrates the impdrtance of ET-l in the development of PH in broilers.7. Long-term (14 days) BQ-123 pretreatment greatly prevented pulmonary hypertension in the broilers exposed in low ambient temperatures (LAT), while LAT led to severe PH in saline and blank groups accompanied by increases in RVSP, PCV, AHI, HR and a decrease in RV |dp/dt|. All these suggest that endothelin-1 play an important role in the development of pulmonary hypertension caused by LAT and that BQ123 ( an ETAR antagonist) may be a new therapeutic agent for LAT-induced pulmonary hypertension in broilers.The study demonstrates considerable similarities in the complex haemodynamic effects of ET-l in chicks. ET-l is one of the factors that regulate the blood vessels rhythm of normal chicks., The study Also indicates ET-l play an important role in development of PH in broilers and BQ123 can prevent PH. Accordingly Future studies are needed to show whether desensitization or upregulation/downregulation of the ETAR may contribute to the increase in circulating ET-l levels in pulmonary hypertension in broilers. The blockage of the ETAR pathway by BQ123 is,a new way to reduce更多还原