Egger M, Donath E, Ziemer S, Glaser R
Biochim Biophys Acta. 1986 Sep 25;861(1):122-30. doi: 10.1016/0005-2736(86)90378-0.
The measurement of the spin of cells in rotating high-frequency electric fields ('electrorotation') make possible the investigation of dielectric membrane properties of single cells. This method was applied to membrane permeability changes accompanying thrombocyte activation and compared with light-scattering data. Describing the dielectric behavior of platelets by a single-shell model and assuming a sufficiently low membrane conductivity of 1 X 10(-7) S/m we found for nonactivated platelets a membrane capacity of 5.5 mF/m2 and the conductivity of the internal medium was estimated to be 0.12 S/m. Upon activation, the electrorotation decreased continuously, with half-times in the range of few minutes. This could be explained assuming a 500-fold increase in membrane conductivity. The application of both local anesthetics and virostatics inhibited the decrease of electrorotation, as did hypertonic osmotic pressure. In all cases this was accompanied by inhibition of platelet aggregation. Hypotonic solutions induced self-aggregation and spontaneous loss of electrorotation. It was concluded that the increase in permeability of the granule membrane is a crucial step in the release reaction and that the electrorotation method is able to detect the incorporation of the granule membranes into the plasma membrane during activation. The advantage of this electrorotation method is that it enables measurements on a single-cell level, thus avoiding interactions between platelets.
测量细胞在旋转高频电场中的自旋（“介电旋转”）使得研究单细胞的介电膜特性成为可能。该方法被应用于伴随血小板激活的膜通透性变化，并与光散射数据进行比较。通过单壳模型描述血小板的介电行为，并假设膜电导率足够低，为1×10（-7）S/m，我们发现未激活的血小板膜电容为5.5 mF/m2，内部介质的电导率估计为0.12 S/m。激活后，介电旋转持续下降，半衰期在几分钟范围内。这可以通过假设膜电导率增加500倍来解释。局部麻醉剂和抗病毒药物的应用均抑制了介电旋转的下降，高渗渗透压也有同样的效果。在所有情况下，这都伴随着血小板聚集的抑制。低渗溶液诱导自聚集和介电旋转的自发丧失。得出的结论是，颗粒膜通透性的增加是释放反应中的关键步骤，并且介电旋转方法能够检测激活过程中颗粒膜并入质膜的情况。这种介电旋转方法的优点是它能够在单细胞水平上进行测量，从而避免血小板之间的相互作用。
