血清α_1-抗胰蛋白酶(α_1-AT)是由肝脏合成的糖蛋白,它能抑制胰蛋白酶、弹性蛋白酶、胶原酶和人白细胞中来的水解酶。Harris等发现肺癌血清中α_1-AT含量高于正常。血管紧张素转化酶(ACE)是由肺血管内皮细胞所产生并直接进入肺循环的。它是将血管紧张素Ⅰ转化成活性的血管紧张素Ⅱ。Liebeman等观察到肺癌病人血清中ACE水平较低于正常。由于α_1-AT不仅在肺癌患者的血清中 Serum α 1 -antitrypsin (α 1 -AT) is a glycoprotein synthesized by the liver that inhibits the hydrolysis enzymes of trypsin, elastase, collagenase, and human leukocytes. Harris et al. found that the levels of α 1 -AT in lung cancer were higher than normal. Angiotensin converting enzyme (ACE) is produced by the pulmonary vascular endothelial cells and enters the pulmonary circulation directly. It is angiotensin II that converts angiotensin I into activity. Liebeman et al. observed that serum ACE levels in lung cancer patients were lower than normal. Since α_1-AT is not only in the serum of lung cancer patients