微粒空氣污染物對心臟功能不全大鼠之心血管研究： 1. 柴油引擎微粒對自發性高血壓鼠之心室功能毒性探討 2. Isoproterenol 誘發左心室功能不全大鼠模式建立

Abstract

柴油引擎微粒對自發性高血壓鼠之心室功能研究 目的：雖然有流行病學研究指出，空氣污染中的微粒和心衰竭的死亡率及急診入院率有關，但結果並不一致。近來有研究指出，罹患心衰竭的病人對於粒徑2.5微克以下的微粒（PM2.5）特別敏感，但作用機轉仍不清楚，所以我們進一步用動物實驗來探討其因果關係。 方法：利用14及16月大的雄性自發性高血壓大鼠作為研究心衰竭之動物模式，以氣管灌注方式，每隔二週分別暴露生理食鹽水(控制組，N=12)及柴油引擎微粒(DEP) 500μg/rat (N=12)共三次。在灌注前後，利用心臟超音波技術測量左心室舒張期（LVDd）和收縮期（LVSd）的內徑，及心室短縮分率（FS）的改變評估左心室功能，並觀察六週內暴露組及控制組的存活率差異。 結果：暴露DEP的大鼠其最後存活率較暴露生理食鹽水之大鼠來的低(50% v.s. 67%)，但無統計上差異。在心臟超音波方面，發現暴露DEP後之高血壓大鼠較暴露前有較低的FS（55.7% v.s. 45.45%， p<.05），及較大的LVDd(0.56cm v.s.0.49cm，p=.056）。 結論：結果顯示柴油引擎微粒可能使原本左心室受損之個體其左心室功能更加惡化，這些發現支持流行病學研究之結果。 Isoproterenol 誘發左心室受損大鼠模式建立 目的：流行病學研究已證實空氣中的微粒濃度與心衰竭入院的發生率有正相關，為了探空氣微粒與心衰竭的因果關係，須建立一可行的心室功能受損之疾病動物模式，並評估此模式之心臟功能及受損程度。 方法：利用20隻八週大之雄性Wistar大鼠，連續兩天皮下施打isoproterenol 150mg/kg (實驗組; n=16)及IDD water (對照組; n=4)。於三週後抽取尾部靜脈血，並在六週後以心臟超音波評估左心室舒張期（LVDd）和收縮期（LVSd）的內徑，及心室短縮分率（FS）後進行犧牲，並抽取血液及摘除心臟。後續將利用ELISA來量測血液中第三週和第六週之BNP濃度。並觀察六週內實驗組及控制組的存活率差異。 結果：施打isoproterenol之實驗組24小時死亡率及總死亡率分別為43.75%及50%。心臟超音波部份，實驗組之FS (35.25%)低於控制組的FS (44.59%)，並達到統計上的意義 (p=0.0197)。實驗組血液中的BNP濃度，於打藥後由第三週0.359 ng/ml增加到第六週的0.435 ng/ml，亦達到統計上意義 (p=0.0001)。 結論：本研究成功利用八週大雄性Wistar大鼠，連續兩天施打isoproterenol 150mg/kg。於六週後，大鼠有心肌受損及左心室功能下降的情形，為一可行之左心室受損之動物模式。

Decreased left ventricular function in spontaneously hypertensive rats exposed to diesel exhaust particles Objective: Epidemiologic studies have shown that the death and hospital admissions of heart failure are associated with particulate matter, but the association is not consistent. Resent studies reported that patients with heart failure were more sensitive to particulate matter with median aerodynamic diameter <2.5μg/m3 (PM2.5). Here, we conducted an animal study to further investigate the causal relationship between diesel exhaust particles (DEP) exposure and left ventricular function. Method: A total of 24 14- or 16-month-old male spontaneously hypertensive rats (SHR) were exposed intra-tracheally to DEP of 500μg/rat (n=12) and saline as the control (n=12) every 2 weeks for three times. Left ventricular systolic (LVDs) and diastolic (LVDd) diameter and the fraction shortening (FS) were measured before and after treatment using echocardiography. Result: Compared to the control group, DEP exposed SHRs have lower survival rate (50% v.s. 67%), but this did not reach a statistic signification. After DEP exposure, FS in SHR was decreased from 55.7% to 45.5% (p<0.05), and LVDd was increased from 0.49 cm to 0.56cm (p=.056). The change of these values in control group was statistically insignificant. Conclusion: Our results suggest that DEP may impair LV function, which may lead to decompensation in subjects with existing LV impairment. The findings also support previous epidemiology studies. Establishment of a left ventricle-dysfunction animal model induced by isoproterenol Objective: Epidemiologic studies showed that the increasing hospital admissions for heart failure are associated with the concentration of particulate matter in the air. In order to investigate the underlying mechanism, it is needed to establish an appropriate animal model of left ventricular impairment, and further to evaluate the function and the degree of impairment. Method: A total of 20 8-week-old male Wistar rats randomly received 150 mg/kg isoproterenol (ISO group, n=16) or IDD water (control group, n=4) twice for 2 days. Rat was drawn blood from each tail vain at 3 weeks after injection. At 6 weeks after injection, rats were assessed the left ventricular diastolic diameters (LVDd) and fractional shortening (FS) by echocardiography, and sacrificed to get the blood and the heart. The BNP concentration of blood was measured by ELISA. We also observed the difference of mortality between ISO and control groups during experimental period. Result: The immediate (24-hour) and total mortality were 43.75% and 50% in ISO group. In echocardiography, the FS of ISO group (35.25%) was lower than that of control group (44.59%) significantly (p=0.0197). The concentration of blood BNP was increased from 0.359 ng/ml to 0.435 ng/ml (p=0.0001) in the ISO group at 3 to 6 weeks after injection. Conclusion: This study successfully established the left ventricle-dysfunction animal model by using 8-week-old male Wistar rats received 150 mg/kg isoproterenol twice for 2 days, and rats were myocardial impaired and decreased LV function at 6 weeks after injection.