A mechanism for the increased activity of α-amylase in serum upon radiation exposure

α-淀粉酶(EC.3.2.1.1)催化淀粉等多糖中α-1.4型葡聚糖键的特异性断裂。α-淀粉酶由胰腺(P-淀粉酶)和唾液腺(S-淀粉酶)产生。众所周知，包括辐射和大手术在内的应激会增加血清中α-淀粉酶的水平。此外，在东海村危重事故中暴露于高剂量辐射的工人中，观察到α-淀粉酶水平升高，他们出现了痛苦的双侧腮腺肿胀。然而，其机制尚不完全清楚。在这项研究中，我们研究了辐射照射导致血液中α-淀粉酶水平和活性增加的机制。3.5Gy3.5Gy14Gy射线照射后，C3H/He小鼠血浆α-淀粉酶活性呈剂量依赖性增加。照射后12h，α-淀粉酶水平最高，约为对照组的3倍，此后，α-淀粉酶水平在照射后24小时降至对照小鼠…的2倍左右更多的妈妈。非变性聚丙烯酰胺凝胶分级和淀粉-碘染色表明，辐照后酶活性升高以S淀粉酶为主，β-淀粉酶不受影响。另一方面，辐射可抑制匹罗卡品引起的唾液流率增加，降低唾液α-淀粉酶活性。此外，腮腺导管结扎导致血液中α-淀粉酶活性增加约3倍。我们通过蛋白质印迹分析和RT-PCR法检测了辐射是否增加了人唾液腺细胞系HSY中α-淀粉酶的产量。当HSY细胞在Matrigel上培养时，这些细胞分化为更成熟的细胞，形成腺泡结构。照射不能提高α-淀粉酶的活性或表达水平。我们从小鼠腮腺制备了腺泡细胞，并进行了体外培养。辐射降低了原代培养细胞的α-淀粉酶活性，提高了培养上清液的活性。照射对细胞凋亡无明显影响。抗淀粉酶抗体染色的细胞显微镜图像显示，辐射使荧光强度降低。此外，将辣根过氧化物酶(HRP)作为示踪剂逆行通过大鼠腮腺的主要排泄管。该示踪剂存在于受辐射大鼠的细胞中，但不存在于对照大鼠的细胞中。当静脉注射HRP时，紧密连接阻止示踪剂从腺泡管腔和细胞内小管进入细胞间隙。然而，在一只受辐射的老鼠身上检测到了该示踪剂。我们的结果提示，辐射可能通过影响紧密连接屏障功能而不改变血液中α-淀粉酶的产生而导致其水平升高；辐射引起的淀粉酶通过牵张屏障释放到血管中。较少

α-amylase (EC.3.2.1.1) catalyzes the specific cleavage of α-1.4 glucan bonds in polysaccharides such as starch. α-amylase is produced by the pancreas (P-amylase) and the salivary glands (S-amylase). Stresses including radiation and major surgery are known to increase the levels of α-amylase in serum. Moreover, increased levels of α-amylase were observed in workers who were exposed to high-dose radiation in the Tokai-mura criticality accident, and they developed a painful bilateral swelling of the parotid glands. However, the mechanism is not fully understood. In this study, we examined mechanisms for the increased level and activity of α-amylase in blood by radiation exposure. Irradiation with doses of 3.5 to 14 Gy increased α-amylase activity in C3H/He mouse plasma in dose-dependent manner. A maximal level of α-amylase was observed at 12 h after irradiation (about 3-fold), and after that, level of α-amylase was decreased to about 2-fold at 24 h compared with that of control mouse plas … More ma. Non-denatured polyacrylamide gel fractionation of the plasma followed by starch-iodine staining showed that S-amylase was dominant in the increased activity by irradiation and P-amylase was not affected. On the other hand, irradiation inhibited increase in the flow rate of saliva induced by pilocarpine and decreased the α-amylase activity in saliva. Furthermore ligation of parotid-duct resulted in the increased α-amylase activity to about 3-fold in blood. We tested whether irradiation increases the production of α-amylase in a human salivary gland cell line HSY by western blot analysis and RT-PCR. When the HSY cells cultured on Matrigel, these cells differentiated into more mature cells ; they formed acinar structure. Irradiation failed to increase the activity or the mRNA level of α-amylase in these HSY cells. We prepared acinar cells from the parotid glands of mice and cultured them in vitro. Irradiation decreased the α-amylase activity in these primarily cultured cells and increased the activity in the culture supernatants. Irradiation did not affect apoptosis. Microscope images of cells stained with anti-amylase antibody showed that irradiation decreased the fluorescence intensities. Furthermore, horseradish peroxidase (HRP) was administered retrogradely as a tracer via a main excretory duct of parotid gland in a rat. The tracer was present in cells from an irradiated rat but not in a control rat. When HRP was injected intravenously, the tight junction prevented the passage of tracer from acinar lumina and intracellular canaliculi into the intercellular space in a control rat. However, the tracer was detected in an irradiated rat. Our results suggest that irradiation may cause increased levels of α-amylase in blood by not altering its production but affecting barrier function of tight junction ; amylase is released into blood vessels through distracted barrier by irradiation. Less