凝血酶对荧光标记的人单个血小板游离［Ca^（2＋）］和膜电位的动态影响

EFFECT OF THROMBIN ON CYTOSOLIC CALCIUM AND MEMBRANE POTENTIAL IN SINGLE HUMAN PLATELETS

本文将ｆｌｕｏ－３和ｄ_ｉ－ＢＡ－Ｃ４（３）荧光标记的血小板固定于纤维蛋白原表面，以５７０型粘附式细胞仪（ＡＣＡＳ５７０）动态观察了凝血酶激活的人单个血小板细胞内游离［Ｃａ^（２＋）］（钙离子浓度）和膜电位的变化。静息状态时细胞游离［Ｃａ^（２＋）］和膜电位荧光较低，波动不明显。当加入０．１Ｕ／ｍｌ凝血酶激活时，［Ｃａ^（２＋）］（细胞内游离钙离子浓度）与膜电位迅速升高，随后［Ｃａ^（２＋）］出现反复振荡，幅度达约５００荧光单位，而膜电位基本上保持峰值水平。［Ｃａ^（２＋）］_ｉ升高与膜电位变化在时间和程度上不一致。本文结果提示，凝血酶引起血小板［Ｃａ^（２＋）］振荡和膜去极化，后者不是Ｃａ^（２＋）内流引起的。

Fluo-3 and di-BA-C4 (3) -loaded human platelets were immobilized on a fibrinogen-coated surface and the cytosolic free [Ca(2+)]i and the membrane potentials were measured in single thrombin-activated platelets by ACAS-570 (Adherent Cell Analysis and Sorting Cytometer). Fluorescence of fluo-3 and di-BA-C4 (3) was low in rest immobilizedplatelets without obviously repetitive spiking. When the platelets were activatedby thrombin, a rapid rise of cytosolic [Ca(2+)]i and membrane potential was observed. Subsequently, oscillations in [Ca(2+)]i to an extent of about 500 fluorescent units were observable, whereas the membrane potential remained at the peak level, i. e, the change of [Ca(2+)]i in no way of accord with that membrane potential. The above resuitsindicate that the thrombin induced membrane depolarization is not due to influx of Ca2+.