Modesti P A, Abbate R, Gensini G F, Colella A, Serneri G G
Clinica Medica I, University of Florence, Florence, Italy.
Eicosanoids. 1990;3(3):139-43.
The kinetics of the binding of TxA2 and the characteristics of its putative uptake by platelets (plt) were investigated with a radiolabelled structural TxA2 analogue, 125I-PTA-OH, in platelets from 6 male healthy volunteers. The kinetic constants (Kobs, K1 and K-1) were calculated by time-course experiments according to Weiland and Molinoff. The affinity constant (Km) and maximal uptake velocity (Vmax) values for each subject were determined by the double-reciprocal plot of Lineweaver-Burk. The kinetically determined dissociation constant Kd was 10 nmol/l. In the uptake experiments a saturability of the association rate of the non-displaceable binding was observed at increased ligand concentration. Michaelis-Menten type kinetics were obtained and the Vmax was 32.44 fmol/10(8) plt x hour with a Km of 6.39 nmol/l. These observations suggest that the uptake was a carrier-mediated active transport.
利用放射性标记的血栓素A2（TxA2）结构类似物125I-PTA-OH，对6名男性健康志愿者血小板中TxA2的结合动力学及其假定的摄取特性进行了研究。根据韦兰德和莫利诺夫的方法，通过时间进程实验计算动力学常数（Kobs、K1和K-1）。通过Lineweaver-Burk双倒数图确定每个受试者的亲和常数（Km）和最大摄取速度（Vmax）值。动力学测定的解离常数Kd为10 nmol/l。在摄取实验中，在配体浓度增加时观察到不可置换结合的缔合速率具有饱和性。获得了米氏动力学类型，Vmax为32.44 fmol/10(8) 血小板×小时，Km为6.39 nmol/l。这些观察结果表明摄取是一种载体介导的主动转运。
