新生鼠缺氧缺血时脑TPA活性与微血管基膜的相关性研究

CORRELATION WITH ACTIVITY OF TISSUE-TYPE PLASMINOGEN ACTIVATOR AND EXTRACELLULAR MATRIX IN BRAIN OF NEONATAL RATS ON HYPOXIA ISCHEMIA

为了探讨缺氧缺血时脑内组织型纤溶酶原激活物 (TPA)与脑微血管基膜降解的相关性 ,本研究采用了下述二种方法 :第一组是将一日龄 SD大鼠分为五组 :(1)空白对照组 ,(2 )假手术组 ,(3 )缺氧缺血组 ,(4 )缺氧缺血后复氧 2 4h组 ,(5 )缺氧缺血后复氧 48h组 ,每组 12只。每组取 4例测 TPA活性和 8例鼠脑用抗 型胶原、层粘连蛋白和纤维粘连蛋白抗体标记。第二组是脑微血管内皮细胞和星形胶质细胞体外培养 :分为 (1)空白对照组 ,在常规条件下培养的细胞 ;(2 )缺氧组 ,在培养液表面覆盖无菌医用液体石蜡 ,形成缺氧环境 ,每组取 8例培养液测 TPA活性。结果证明 ,在三个实验组中以缺氧缺血组的 TPA活性最高 ,而后随着复氧时间的增加而下降。培养的内皮细胞缺氧组 TPA活性比对照组高 ,而星形胶质细胞缺氧组 TPA活性与对照组无差别。三个实验组的 型胶原、层粘连蛋白和纤维粘连蛋白阳性染色平均单位面积较两对照组者小。三个实验组阳性产物呈不连续线状的微血管数较两对照组多。以上结果显示 ,缺氧缺血可激发新生大鼠脑内 TPA活性增高 ,主要是脑微血管内皮分泌的 TPA活性增高 ,然后通过一系列酶促反应 ,使微血管基膜的细胞外基质成分— 型胶原、层粘连蛋白和纤维粘连蛋白等降解 ,血脑屏障受损 ,微血管的渗透性增?

The effect of tissue type plasminogen activator (TPA) in hypoxic ischemic brain damage was investigated in the present study. Neonatal SD rats were divided into (1) control group, (2) operation group, (3) hypoxic ischemic group, (4) survived in 24 hours after hypoxic ischemic group, (5) survived in 48 hours after hypoxic ischemic group; n=12 in each group. Cerebral tissues of 4 brains in each group were measured in activity of TPA. And 8 cerebra of each group were marked with antibodies against type Ⅳ collagen, laminin and fibronectin. The activity of TPA in two control groups was lower than that in three experimental groups (P<0.01). The activity of TPA in hypoxic ischemic group was the highest among the three experimental groups, and survived in 48 hours group was the lowest among the three experimental groups (P<0.01). Average areas of positive staining of three antibodies around microvessels in the three experimental groups were less than that in two control groups (P< 0.01 ). The microvessel count of discontinuous positive staining in three experimental groups was more than that in two control groups (P<0.01). The brain weight of hypoxic ischemic group was the weightiest among five groups (P<0.05), which the cerebral edema in the group appeared. The brain weight of survived in 24 hours group was lighter than that of hypoxic ischemic group (P<0.05). The brain weight of survived in 48 hours group was comparable to that of two control groups. Our study showed that hypoxia ischemia can stimulate to raise the activity of TPA in the brain of rats. Then it resulted in that extracellular matrix type Ⅳ collagen, laminin and fibronectin were degraded with a series of enzyme induction reaction, and damaged the basement membrane of cerebral microvessels. The permeability of microvessels was increased, and edema of brain occurred.