茶多酚对重复+Gz暴露大鼠心功能和心肌超微结构的影响
作者：詹 皓 董华进 辛益妹 唐桂香
单位：詹 皓.空军航空医学研究所，北京 100036
关键词：加速度应激(生理)；心功能；心肌；茶多酚；超微结构；大鼠
航天医学与医学工程990201Effects of Tea Polyphenols on Cardiac Function and Myocardial
Ultrastructure in Rats after Repeated +Gz Stress
ZHAN Hao1,DONG Hua-jin2，XIN Yi-mei1，TANG Gui-xiang1
, 百拇医药
(1.Institute of Aviation Medicine, Beijing 100036;2.Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850)
Abstract: Objective To observe the effects of tea polyphenols (TP) on cardiac function and myocardial ultrastructure in rats after repeated +10 Gz stress. Method Twenty four male Wistar rats were randomly divided into three groups (n=8 each): group A (control), group B (+10 Gz), group C (+Gz with TP). Group B and C were repeatedly exposed to +10 Gz (each for 30 s, onset rate about 0.5 G/s, 3 times/d with +1 Gz 1 min intervals, 3 d/wk, 4 weeks in total), but group A was only submitted to +1 Gz. TP(200 mg.kg-1) was given orally to group C about 1h prior to the +Gz experiment, and distilled water was given to group A and B.Function of isolated rat working hearts and myocardial ultrastructure were observed. Result A significant decrease of left ventricular systolic pressure (LVSP) and injury of myocardial structure in rats were demonstrated after repeated +10 Gz stress. But TP could remarkably elevate the LVSP and improve myocardial ultrastructural injury in +10Gz stressed rats. Conclusion These results indicated that repeated high G exposure may produce cardiac structural and functional injuries in rats which might be partly related to free radical metabolism; and antioxidant TP had significant protective effects on the hearts of +Gz stressed rats.
, 百拇医药
Key words：acceleration stress(physiology);heart function;myocardium;tea polyphenols;ultrastructures;rats;
摘要：目的 观察天然抗氧化剂茶多酚(Tea polyphenols, TP)对重复+10Gz暴露大鼠心功能和心肌超微结构的影响。方法 24只雄性Wistar大鼠随机等分为三组(n=8)：A组(对照组),B组(+10 Gz组)，C组(TP组)。B、C组受重复+10 Gz作用(每次峰值30s，G增长率约为0.5G/s，3次/d，间隔+1 Gz/min，3d/wk,共4wk)，而A组仅受+1Gz 作用。C组于+Gz实验前约1h灌胃给予TP(200mg.kg-1)，另两组给予等量蒸馏水。 测定离体大鼠工作心脏的心功能并用电镜观察心肌超微结构的变化。结果 与对照组相比，重复+10Gz暴露使大鼠左室内压峰值(LVSP)明显降低， 心肌细胞超微结构出现明显损伤； 而TP可显著提高+10Gz应激大鼠的LVSP并使心肌超微结构损伤明显减轻。结论 重复高G作用可致大鼠心功能和结构损伤，其作用机理可能部分与自由基代谢有关； 而天然抗氧化剂TP对此具有明显防护作用。
, http://www.100md.com
中图分类号：R852.21 文献标识码：A 文章编号：1002-0837(1999)02-0079-05
Many studies have demonstrated that repeated high sustained +Gz exposure can induce myocardial metabolic, functional and structural changes in experimental animals[1～3]. French investigators reported echocardiographic findings of increased right ventricular dimensions in Mirage 2000 pilots as compared with a control group of transport pilots[4]. In another study they reported that there was no such difference, and suggested that these data were valid only in current crew flying the current generation of fighter[5].However,Tomorrow's fighter pilots may expect significantly greater G forces with more rapid onset.Up to date, anti-G methods mainly include anti-G garments and anti-G maneuvers aiming to prevent G-LOC. Therefore, how to improve the myocardiol metabolism and protect the cellular structure after repeated high +Gz stress so as to elevate the function of cardiovascular system of aircrew is very important in military aviation medicine.Our previous investigations showed that natural antioxidant tea polyphenols (TP) could significantly increase the cardiac function in rats, modulate energy metabolism in mouse brain, and have anti-fatigue effect in mice[6].In this study, the effects of TP on cardiac function and myocardial ultrastructure of rats after repeated +10 Gz stress were further observed.
, 百拇医药
Methods
Experimental animal and drug administration Male Wistar rats (193.3±14.2 g,n=24) from the Experimental Animal Center, Chinese Academy of Military Medical Sciences served as experimental subjects. These animals were randomly divided into three groups (n=8 each): A (control), B (+10 Gz) and C (+Gz with TP) . About 1h prior to the +Gz experimert TP(200 mg/kg) was given orally in group C; while distilled water was given to group A and B. TP (concentration>97%) was produced by Hangzhou Dongya Tea Polyphenol Factory.
, 百拇医药
+Gz stress profile Rats (without anesthethia) were restrained in a special frame 3cm in diameter, 10cm in length. The rate of +Gz onset was about 0.5G/s. Both group B and C were exposed to repeated +10Gz stress (each for 30s, 3times/d with +1Gz/min intervals, 3d/wk, 4wk in total ); and the rats in group A were handled in the same way but only submitted to +1Gz.
Measurement of function of isolated working rat hearts Eighteen hearts (6 from each group) were isolated in the next day after the last centrifuge run. The hearts were perfused according to our previous methods[7]. Left ventricular systolic pressure (LVSP) was measured with a pressure transducer through a small plastic cannula passed via aorta. The pressure developed by the left ventricle (LVDP)was the difference between the systolic and the diastolic pressure. In addition, heart rate (beats/min) and coronary flow (ml/min) were recorded, and the maximal rate of rise and fall in LVSP (±dp/dtmax) were calculated with a computer according to LVSP signal.
, http://www.100md.com
Examination of myocardial ultra structure of rat hearts Two hearts from each group were isolated in the next day after the last centrifuge run, and a small piece of myocardum was immediately dissected from each cardiac apex (left ventricle) for ultrastructural examination. These samples were prepared with routine method and examined using a JEM-1200EX transmission electron microscope in the National Center of Biomedical Analysis, Academy of Military Medical Sciences.
, http://www.100md.com
Results
Effects of TP on cardiac function in rats after repeated +10Gz stress(Table 1) Myocardial constructive ability was significantly damaged after repeated +10Gz stress, but TP could remarkably elevate the LVSP (compared with group B at 30, 45 and 60 min during perfusion,P<0.05). There were no significant differences of heart rate, aortic flow, coronary flow and -dp/dtmax among the three groups.
Table 1 Effects of TP on cardinc function in rats after repeated +10Gz stress (
±s,n=6) Group
, http://www.100md.com
During perfusion after +10 Gz stress(min)
5
30
45
60
LVSP
A
11.15±0.71
11.83±0.83
11.83±0.37
11.61±0.41
(kPa)
, http://www.100md.com
B
10.27±0.85*
10.72±0.66*
11.00±0.50**
10.38±0.62**
C
10.78±1.23
11.92±1.19#
11.94±0.10#
11.74±1.09#
, 百拇医药
LVDP
A
10.92±0.81
11.57±0.62
11.53±0.62
11.35±0.45
(kPa)
B
10.14±1.07*
10.56±0.85**
10.90±0.64*
, http://www.100md.com
10.32±0.89*
C
10.24±1.07
11.57±1.25
11.59±1.09
11.39±1.09#
RPP
A
2439±166
2435±431
2446±306
2518±375
, 百拇医药
B
1943±220**
2287±227
2344±187
2118±238*
C
2387±209##
2506±299
2584±288
2520±328#
+dp/dtmax
, 百拇医药
A
374.7±21.4
387.8±30.6
387.8±45.0
405.2±46.0
(kPa/s)
B
324.2±45.6*
371.2±34.7
371.2±41.8
371.2±38.4
C
, 百拇医药
348.5±35.8
396.5±30.6
413.9±38.5#
392.2±46.8
Notes:RPP(kPa.beats/min): LVSP×HR;*P<0.05,**P<0.01,as compared with A; #P<0.05,##P<0.01,as compared with B
Effects of TP on myocardial ultra structure in rats after repeated +10 Gz stress As compared with the control (Fig.1),a significant myocardial ultrastructural injury was observed after repeated +10 Gz stress (Fig.2, Fig.3), whereas TP had significant protective effect on the cellular structural injury (Fig.4).
, http://www.100md.com
Fig.1 Normal myocardial cells of rat (longitudinal section of muscle segment). Z lines, M lines, a lot of mitochondria, glycogen granules and nuclei were shown(×10000×0.5)
Fig.2 Myocardial fibers were loose and breaking after repeated +10 Gz stress(×17000×0.5)
Fig.3 Myocardial mitochondria were heavily damaged after repeated +10Gz stress(×13000×0.5)
, 百拇医药
Fig.4 Compared with +10 Gz group, TP had significant protective effect on myocardial mitochondrial injury and maintainted muscle segment nearly normal (×10000×0.5)
Discussion
Many studies have been carried out to explore the effects of high sustained +Gz on heart and the effective mechanisms. Burton and MacKenzie observed ventricular endocardial hemorrhage in +8 Gz or +9 Gz stressed miniswine[1].Dowell et al further investigated the genesis of ventricular hemorrhage in swine[2]. Their results suggested that heart pathology might be mediated by influences other than hypoxia or ischemia, because depressed mitochondrial function would be expected in hearts subjected to hypoxia and/or ischemic insult, but they found the contrary responses: increases in mitochondrial respiratory rate and the rate of calcium transportation. However, myocardial ischemia and /or hypoxia was still one factor of heart injury, because Dowell et al found disruption of myocardial lysosomal membrane integrity in +9 Gz stressed swine, which was usually noted in infarcted heart tissue following coronary artery ligation. The rapid and dramatic increases in lysosomal enzyme activity and in both mitochondrial respiration and calcium transportation activity after acceleration suggested that humoral factors or substances , e.g. catecholamine might be related to the intracellular changes[2], because catecholamine could increase lysosomal enzymatic activities and mitochondrial functions. Harrison[8] observed that humans subjected to short-duration acceleration exposure exhibited elevation in noradrenaline , but he concluded that the complete effect of acceleration-induced myocardial stress was not due solely to a beta-adrenergic response.Tran et al[3] observed that cardiac work was reduced after repeated exposure to +10 Gz acceleration, which could be partly due to altered energy metabolism in rat hearts caused by +Gz stress. The increase in inorganic phosphate might be resulted from the state of increase in cardiovascular sympathetic tone caused by repeated +Gz stress, for example, in baboons, the resting blood level of noradrenaline was even raised at the 24 th exposure to +Gz stress[9].
, 百拇医药
Our results were in accordance with other investigations[3，10]. These results suggested that repeated high G stress could induce the injury of myocardial function of contraction, which might be related to the pathological change of ultrastructure. According to the protective effects of typical antioxidant TP, it was suggested that free radical metobolism was associated with repeated +10 Gz stress induced rat heart injury. The mechanisms might be related to the following factors: +Gz induced myocardial ischemic/reperfusion could activate xanthine oxidase which catalyzed the conversion of hypoxanthine or xanthine and oxygen to xanthine or uric acid, generating a superoxide radical (O-2)[11];the oxygen free radicals are produced as a major mechanism in the production of catecholamine cardiomyopathy[12],and +Gz could significantly increase the blood level of catecholamine[9].In addition, mitochondrial respiration, inflammation (white blood cells), prostaglandin metabolism and other mechanism were also involved in the generation of free radicals and/or interrelate to free radical metabolism. Free radical scavenging effects of TP and its main composites have been proved. After pretreatment of ischemic reperfused rat heart with TP,oxygen free radicals can be reduced by 71%[13].The protective effects of TP on isoprenaline induced heart injury in rats were also demonstrated[14].In addition, TP had cardiac tonic and anti-fatigue effects, and could modulate brain energy metabolism[6].Therefore, the protective effects of TP on repeated +10 Gz stress induced heart injury in rats might be related to its antioxidative ability and other pharmacological actions. However, a further study should be made on the relationship between free radical metabolism and repeated +10 Gz stress induced myocardial injury.
, 百拇医药
References
[1]Burton RD, MacKenzie WF. Heart pathology associated with high sustained +Gz[J].Aviat Space Environ Med, 1975, 46(10): 1251～1253
[2]Dowell RT, Sordahl LA, Lindsey JN et al. Heart biochemical responses in miniature swine subjected to +Gz acceleration[J].Aviat Space Environ Med, 1975,46 (11): 1378～1382
[3]Tran CC, Aussedat J, Ray A et al.Bioenergetic effects of repeated +Gz acceleration on rat heart: 31P-NMR study on isolated hearts[J]. Aviat Space Environ Med, 1996, 67(2):146～152
, 百拇医药
[4]Ille H, Didier A, Allegrini N et al.Selection et Surveillance Medicales des pilotes de Mirage 2000: apport de l'echocardiographie[C].In: AGARD Conference Proceedings Medical Selection and Physiologic Training of Future Fighter Aircrew. CP-396, 1985, 32-1-32-13
[5]AGARD Aerospace Medical Panel Working Group 18. Echocardiographic findings in NATO pilots: do acceleration (+Gz) stress damage the heart[J]? Aviat Space Environ Med, 1997, 68(7): 596～600
, 百拇医药
[6]Dong HJ, Zhan H, Yan XZ et al. Effects of tea polyphenols on cardiac function of isolated working heart in rat, calcium current in cultured rat sympathetic neuron and energy metabolism in mouse brain[J]. 中华航空航天医学杂志, 1997, 8(2): 69～73
[7]董华进，胡定浩. 赛啦嗪对大鼠心功能的影响[J]. 军事医学科学院院刊，1996,20(2):91～93
[8]Harrison MH. Adrenergic beta-receptor blockade and metabolic response to centrifugation stress[J]. J Appl Physiol, 1973,35(6):793～797
, 百拇医药
[9]Liscia P, Drogou C, Quandieu P et al. Effects of high sustained hypergravity on plasma catecholamine[J]. Physiologist, 1990,33(suppl 1):S153～S154
[10]孙喜庆, 蔡建辉, 刘 勇. +Gz作用下免心脏功能的改变[J]. 航天医学与医学工程，1997,10(4)：250～253
[11]Mc Cord JM. Oxygen-derived free radicals in postischemic tissue injury[J]. N Engl J Med, 1985, 312(3):159～163
[12]Flaherty JT, Weisfeldt ML. Reperfusion injury[J]. Free Rad Biol Med,1988,5(6):409～419
[13]邹曦露, 万 谦, 李美芬等. 茶多酚对鼠心肌缺血再灌产生氧自由基的清除[J]. 波谱学杂志，1995,12(3)：237～244
[14]汤圣兴, 叶 艇, 赵振东. 茶多酚对大鼠异丙肾上腺素诱发心肌损伤的保护作用[J].中草药，1995,26(4)：197～198
Recieved date:1998-04-28, 百拇医药
单位：詹 皓.空军航空医学研究所，北京 100036
关键词：加速度应激(生理)；心功能；心肌；茶多酚；超微结构；大鼠
航天医学与医学工程990201Effects of Tea Polyphenols on Cardiac Function and Myocardial
Ultrastructure in Rats after Repeated +Gz Stress
ZHAN Hao1,DONG Hua-jin2，XIN Yi-mei1，TANG Gui-xiang1
, 百拇医药
(1.Institute of Aviation Medicine, Beijing 100036;2.Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing 100850)
Abstract: Objective To observe the effects of tea polyphenols (TP) on cardiac function and myocardial ultrastructure in rats after repeated +10 Gz stress. Method Twenty four male Wistar rats were randomly divided into three groups (n=8 each): group A (control), group B (+10 Gz), group C (+Gz with TP). Group B and C were repeatedly exposed to +10 Gz (each for 30 s, onset rate about 0.5 G/s, 3 times/d with +1 Gz 1 min intervals, 3 d/wk, 4 weeks in total), but group A was only submitted to +1 Gz. TP(200 mg.kg-1) was given orally to group C about 1h prior to the +Gz experiment, and distilled water was given to group A and B.Function of isolated rat working hearts and myocardial ultrastructure were observed. Result A significant decrease of left ventricular systolic pressure (LVSP) and injury of myocardial structure in rats were demonstrated after repeated +10 Gz stress. But TP could remarkably elevate the LVSP and improve myocardial ultrastructural injury in +10Gz stressed rats. Conclusion These results indicated that repeated high G exposure may produce cardiac structural and functional injuries in rats which might be partly related to free radical metabolism; and antioxidant TP had significant protective effects on the hearts of +Gz stressed rats.
, 百拇医药
Key words：acceleration stress(physiology);heart function;myocardium;tea polyphenols;ultrastructures;rats;
摘要：目的 观察天然抗氧化剂茶多酚(Tea polyphenols, TP)对重复+10Gz暴露大鼠心功能和心肌超微结构的影响。方法 24只雄性Wistar大鼠随机等分为三组(n=8)：A组(对照组),B组(+10 Gz组)，C组(TP组)。B、C组受重复+10 Gz作用(每次峰值30s，G增长率约为0.5G/s，3次/d，间隔+1 Gz/min，3d/wk,共4wk)，而A组仅受+1Gz 作用。C组于+Gz实验前约1h灌胃给予TP(200mg.kg-1)，另两组给予等量蒸馏水。 测定离体大鼠工作心脏的心功能并用电镜观察心肌超微结构的变化。结果 与对照组相比，重复+10Gz暴露使大鼠左室内压峰值(LVSP)明显降低， 心肌细胞超微结构出现明显损伤； 而TP可显著提高+10Gz应激大鼠的LVSP并使心肌超微结构损伤明显减轻。结论 重复高G作用可致大鼠心功能和结构损伤，其作用机理可能部分与自由基代谢有关； 而天然抗氧化剂TP对此具有明显防护作用。
, http://www.100md.com
中图分类号：R852.21 文献标识码：A 文章编号：1002-0837(1999)02-0079-05
Many studies have demonstrated that repeated high sustained +Gz exposure can induce myocardial metabolic, functional and structural changes in experimental animals[1～3]. French investigators reported echocardiographic findings of increased right ventricular dimensions in Mirage 2000 pilots as compared with a control group of transport pilots[4]. In another study they reported that there was no such difference, and suggested that these data were valid only in current crew flying the current generation of fighter[5].However,Tomorrow's fighter pilots may expect significantly greater G forces with more rapid onset.Up to date, anti-G methods mainly include anti-G garments and anti-G maneuvers aiming to prevent G-LOC. Therefore, how to improve the myocardiol metabolism and protect the cellular structure after repeated high +Gz stress so as to elevate the function of cardiovascular system of aircrew is very important in military aviation medicine.Our previous investigations showed that natural antioxidant tea polyphenols (TP) could significantly increase the cardiac function in rats, modulate energy metabolism in mouse brain, and have anti-fatigue effect in mice[6].In this study, the effects of TP on cardiac function and myocardial ultrastructure of rats after repeated +10 Gz stress were further observed.
, 百拇医药
Methods
Experimental animal and drug administration Male Wistar rats (193.3±14.2 g,n=24) from the Experimental Animal Center, Chinese Academy of Military Medical Sciences served as experimental subjects. These animals were randomly divided into three groups (n=8 each): A (control), B (+10 Gz) and C (+Gz with TP) . About 1h prior to the +Gz experimert TP(200 mg/kg) was given orally in group C; while distilled water was given to group A and B. TP (concentration>97%) was produced by Hangzhou Dongya Tea Polyphenol Factory.
, 百拇医药
+Gz stress profile Rats (without anesthethia) were restrained in a special frame 3cm in diameter, 10cm in length. The rate of +Gz onset was about 0.5G/s. Both group B and C were exposed to repeated +10Gz stress (each for 30s, 3times/d with +1Gz/min intervals, 3d/wk, 4wk in total ); and the rats in group A were handled in the same way but only submitted to +1Gz.
Measurement of function of isolated working rat hearts Eighteen hearts (6 from each group) were isolated in the next day after the last centrifuge run. The hearts were perfused according to our previous methods[7]. Left ventricular systolic pressure (LVSP) was measured with a pressure transducer through a small plastic cannula passed via aorta. The pressure developed by the left ventricle (LVDP)was the difference between the systolic and the diastolic pressure. In addition, heart rate (beats/min) and coronary flow (ml/min) were recorded, and the maximal rate of rise and fall in LVSP (±dp/dtmax) were calculated with a computer according to LVSP signal.
, http://www.100md.com
Examination of myocardial ultra structure of rat hearts Two hearts from each group were isolated in the next day after the last centrifuge run, and a small piece of myocardum was immediately dissected from each cardiac apex (left ventricle) for ultrastructural examination. These samples were prepared with routine method and examined using a JEM-1200EX transmission electron microscope in the National Center of Biomedical Analysis, Academy of Military Medical Sciences.
, http://www.100md.com
Results
Effects of TP on cardiac function in rats after repeated +10Gz stress(Table 1) Myocardial constructive ability was significantly damaged after repeated +10Gz stress, but TP could remarkably elevate the LVSP (compared with group B at 30, 45 and 60 min during perfusion,P<0.05). There were no significant differences of heart rate, aortic flow, coronary flow and -dp/dtmax among the three groups.
Table 1 Effects of TP on cardinc function in rats after repeated +10Gz stress (
±s,n=6) Group, http://www.100md.com
During perfusion after +10 Gz stress(min)
5
30
45
60
LVSP
A
11.15±0.71
11.83±0.83
11.83±0.37
11.61±0.41
(kPa)
, http://www.100md.com
B
10.27±0.85*
10.72±0.66*
11.00±0.50**
10.38±0.62**
C
10.78±1.23
11.92±1.19#
11.94±0.10#
11.74±1.09#
, 百拇医药
LVDP
A
10.92±0.81
11.57±0.62
11.53±0.62
11.35±0.45
(kPa)
B
10.14±1.07*
10.56±0.85**
10.90±0.64*
, http://www.100md.com
10.32±0.89*
C
10.24±1.07
11.57±1.25
11.59±1.09
11.39±1.09#
RPP
A
2439±166
2435±431
2446±306
2518±375
, 百拇医药
B
1943±220**
2287±227
2344±187
2118±238*
C
2387±209##
2506±299
2584±288
2520±328#
+dp/dtmax
, 百拇医药
A
374.7±21.4
387.8±30.6
387.8±45.0
405.2±46.0
(kPa/s)
B
324.2±45.6*
371.2±34.7
371.2±41.8
371.2±38.4
C
, 百拇医药
348.5±35.8
396.5±30.6
413.9±38.5#
392.2±46.8
Notes:RPP(kPa.beats/min): LVSP×HR;*P<0.05,**P<0.01,as compared with A; #P<0.05,##P<0.01,as compared with B
Effects of TP on myocardial ultra structure in rats after repeated +10 Gz stress As compared with the control (Fig.1),a significant myocardial ultrastructural injury was observed after repeated +10 Gz stress (Fig.2, Fig.3), whereas TP had significant protective effect on the cellular structural injury (Fig.4).
, http://www.100md.com
Fig.1 Normal myocardial cells of rat (longitudinal section of muscle segment). Z lines, M lines, a lot of mitochondria, glycogen granules and nuclei were shown(×10000×0.5)
Fig.2 Myocardial fibers were loose and breaking after repeated +10 Gz stress(×17000×0.5)
Fig.3 Myocardial mitochondria were heavily damaged after repeated +10Gz stress(×13000×0.5)
, 百拇医药
Fig.4 Compared with +10 Gz group, TP had significant protective effect on myocardial mitochondrial injury and maintainted muscle segment nearly normal (×10000×0.5)
Discussion
Many studies have been carried out to explore the effects of high sustained +Gz on heart and the effective mechanisms. Burton and MacKenzie observed ventricular endocardial hemorrhage in +8 Gz or +9 Gz stressed miniswine[1].Dowell et al further investigated the genesis of ventricular hemorrhage in swine[2]. Their results suggested that heart pathology might be mediated by influences other than hypoxia or ischemia, because depressed mitochondrial function would be expected in hearts subjected to hypoxia and/or ischemic insult, but they found the contrary responses: increases in mitochondrial respiratory rate and the rate of calcium transportation. However, myocardial ischemia and /or hypoxia was still one factor of heart injury, because Dowell et al found disruption of myocardial lysosomal membrane integrity in +9 Gz stressed swine, which was usually noted in infarcted heart tissue following coronary artery ligation. The rapid and dramatic increases in lysosomal enzyme activity and in both mitochondrial respiration and calcium transportation activity after acceleration suggested that humoral factors or substances , e.g. catecholamine might be related to the intracellular changes[2], because catecholamine could increase lysosomal enzymatic activities and mitochondrial functions. Harrison[8] observed that humans subjected to short-duration acceleration exposure exhibited elevation in noradrenaline , but he concluded that the complete effect of acceleration-induced myocardial stress was not due solely to a beta-adrenergic response.Tran et al[3] observed that cardiac work was reduced after repeated exposure to +10 Gz acceleration, which could be partly due to altered energy metabolism in rat hearts caused by +Gz stress. The increase in inorganic phosphate might be resulted from the state of increase in cardiovascular sympathetic tone caused by repeated +Gz stress, for example, in baboons, the resting blood level of noradrenaline was even raised at the 24 th exposure to +Gz stress[9].
, 百拇医药
Our results were in accordance with other investigations[3，10]. These results suggested that repeated high G stress could induce the injury of myocardial function of contraction, which might be related to the pathological change of ultrastructure. According to the protective effects of typical antioxidant TP, it was suggested that free radical metobolism was associated with repeated +10 Gz stress induced rat heart injury. The mechanisms might be related to the following factors: +Gz induced myocardial ischemic/reperfusion could activate xanthine oxidase which catalyzed the conversion of hypoxanthine or xanthine and oxygen to xanthine or uric acid, generating a superoxide radical (O-2)[11];the oxygen free radicals are produced as a major mechanism in the production of catecholamine cardiomyopathy[12],and +Gz could significantly increase the blood level of catecholamine[9].In addition, mitochondrial respiration, inflammation (white blood cells), prostaglandin metabolism and other mechanism were also involved in the generation of free radicals and/or interrelate to free radical metabolism. Free radical scavenging effects of TP and its main composites have been proved. After pretreatment of ischemic reperfused rat heart with TP,oxygen free radicals can be reduced by 71%[13].The protective effects of TP on isoprenaline induced heart injury in rats were also demonstrated[14].In addition, TP had cardiac tonic and anti-fatigue effects, and could modulate brain energy metabolism[6].Therefore, the protective effects of TP on repeated +10 Gz stress induced heart injury in rats might be related to its antioxidative ability and other pharmacological actions. However, a further study should be made on the relationship between free radical metabolism and repeated +10 Gz stress induced myocardial injury.
, 百拇医药
References
[1]Burton RD, MacKenzie WF. Heart pathology associated with high sustained +Gz[J].Aviat Space Environ Med, 1975, 46(10): 1251～1253
[2]Dowell RT, Sordahl LA, Lindsey JN et al. Heart biochemical responses in miniature swine subjected to +Gz acceleration[J].Aviat Space Environ Med, 1975,46 (11): 1378～1382
[3]Tran CC, Aussedat J, Ray A et al.Bioenergetic effects of repeated +Gz acceleration on rat heart: 31P-NMR study on isolated hearts[J]. Aviat Space Environ Med, 1996, 67(2):146～152
, 百拇医药
[4]Ille H, Didier A, Allegrini N et al.Selection et Surveillance Medicales des pilotes de Mirage 2000: apport de l'echocardiographie[C].In: AGARD Conference Proceedings Medical Selection and Physiologic Training of Future Fighter Aircrew. CP-396, 1985, 32-1-32-13
[5]AGARD Aerospace Medical Panel Working Group 18. Echocardiographic findings in NATO pilots: do acceleration (+Gz) stress damage the heart[J]? Aviat Space Environ Med, 1997, 68(7): 596～600
, 百拇医药
[6]Dong HJ, Zhan H, Yan XZ et al. Effects of tea polyphenols on cardiac function of isolated working heart in rat, calcium current in cultured rat sympathetic neuron and energy metabolism in mouse brain[J]. 中华航空航天医学杂志, 1997, 8(2): 69～73
[7]董华进，胡定浩. 赛啦嗪对大鼠心功能的影响[J]. 军事医学科学院院刊，1996,20(2):91～93
[8]Harrison MH. Adrenergic beta-receptor blockade and metabolic response to centrifugation stress[J]. J Appl Physiol, 1973,35(6):793～797
, 百拇医药
[9]Liscia P, Drogou C, Quandieu P et al. Effects of high sustained hypergravity on plasma catecholamine[J]. Physiologist, 1990,33(suppl 1):S153～S154
[10]孙喜庆, 蔡建辉, 刘 勇. +Gz作用下免心脏功能的改变[J]. 航天医学与医学工程，1997,10(4)：250～253
[11]Mc Cord JM. Oxygen-derived free radicals in postischemic tissue injury[J]. N Engl J Med, 1985, 312(3):159～163
[12]Flaherty JT, Weisfeldt ML. Reperfusion injury[J]. Free Rad Biol Med,1988,5(6):409～419
[13]邹曦露, 万 谦, 李美芬等. 茶多酚对鼠心肌缺血再灌产生氧自由基的清除[J]. 波谱学杂志，1995,12(3)：237～244
[14]汤圣兴, 叶 艇, 赵振东. 茶多酚对大鼠异丙肾上腺素诱发心肌损伤的保护作用[J].中草药，1995,26(4)：197～198
Recieved date:1998-04-28, 百拇医药