Gilboa N, Kaplan J E
Thromb Haemost. 1985 Oct 30;54(3):639-44.
The effects of plasma fibronectin on the fibrinolytic system were studied in vitro. Fibronectin caused a time and concentration-dependent increase (up to 99% with 330 micrograms/ml) in the amidolytic activity of tissue plasminogen activator (TPA) but not of urokinase. In the presence of fibronectin the Km of the amidolytic activity of TPA decreased without a change in Vmax. It also caused a concentration-dependent increase in lys-plasminogen activation by TPA (up to 825% with 375 micrograms/ml) and by urokinase (up to 400% with 250 micrograms/ml), as well as in the amidolytic activity of plasmin (up to 55% with 300 micrograms/ml). Fibronectin did not enhance the activation of glu-plasminogen. In the presence of fibronectin the Km of lys-plasminogen activation decreased without a change in Vmax. In purified systems fibronectin significantly shortened the clot lysis time (CLT) by up to 28% and 30% in TPA- and plasmin-activated lysis, respectively. The presence of Ca2+ did not change fibronectin's effect on CLT. Clots of non-fibronectin-depleted plasma were lysed up to about twice as fast as the clots of fibronectin-depleted plasma. In conclusion, physiologic concentrations of fibronectin enhanced the fibrinolytic system in vitro. Further studies will be required to elucidate the mechanisms involved and to document whether fibronectin has a similar effect in vivo.
体外研究了血浆纤连蛋白对纤溶系统的影响。纤连蛋白使组织型纤溶酶原激活剂（TPA）的酰胺水解活性呈时间和浓度依赖性增加（330微克/毫升时增加高达99%），但对尿激酶无此作用。在纤连蛋白存在的情况下，TPA酰胺水解活性的Km降低，而Vmax不变。它还使TPA（375微克/毫升时增加高达825%）和尿激酶（250微克/毫升时增加高达400%）介导的赖氨酸纤溶酶原激活以及纤溶酶的酰胺水解活性（300微克/毫升时增加高达55%）呈浓度依赖性增加。纤连蛋白不会增强谷氨酸纤溶酶原的激活。在纤连蛋白存在的情况下，赖氨酸纤溶酶原激活的Km降低，而Vmax不变。在纯化系统中，纤连蛋白在TPA激活的溶解和纤溶酶激活的溶解中分别使凝块溶解时间（CLT）显著缩短高达28%和30%。Ca2+的存在不会改变纤连蛋白对CLT的影响。未去除纤连蛋白的血浆凝块的溶解速度比去除纤连蛋白的血浆凝块快约两倍。总之，生理浓度的纤连蛋白在体外增强了纤溶系统。需要进一步研究以阐明其中涉及的机制，并证明纤连蛋白在体内是否有类似作用。
