Platelet volume and Electrophoretic Mobility in Thrombosis

Abstract

Platelets in circulation are not homogenous in size, density, metabolism and responsiveness to ADP or collagen. The platelet carries a net negative surface charge and its change may be an important factor in platelet adhesion and aggregation. Platelet volume has also been related to the functions. In this paper role of the platelet volume and the electrophoretic mobility in thrombus formation was studied.Materials and Methods: Twelve male rabbits of Japanese white strain were used. Eight were controls and 4 were injected with ADP 2mg/kg into the central vein in several seconds and pulmonary thrombosis was induced under an intravenous pentobarbital anesthesia. Blood, 50ml, was withdrawn from both groups into EDTA containing syringes through a femoral arterial cannula. Platelet rich plasma was washed twice in Tris-NaCl buffer and suspended in 3mM triethanolamine acetate buffer. Platelet electrophoresis was performed with a Continuous Free-Flow Electrophoresis VAP-5 (Bender & Hobein, Munich) at 18°C, 1, 250V and 80mA. Approximately 5×108 platelets were electrophoresed per hour. The fraction #1 is an anode side and #90 a cathode side. Platelets in each fraction suspended in the buffer were studied for platelet count and volume determinations by a Coulter counter ZbI and a channelyzer C-1000.Results: Control platelets were separated well making a single peak at the 20.9±2.6 fraction (Fig. 1). In acute thrombosis the peak was at the 15.5±1.4 fraction (Fig. 2) and the curve is shifted to the anode side as compared with the control (p<0.10). The mode platelet volume increased as the fraction number increased in the control (Fig. 3), but this trend disappeared in the thrombosis and the mode volume was almost same throughout the fractions at the level of anode side fractions of the control (Fig. 4).Discussion: Hampton and Mitchell reported that platelets exposed to ADP of low concentration increased the electrophoretic mobility and this might be the explanation of the increased mobility of the platelets which were saved from thrombus formation. The reduction in electrophoretic mobility of the platelets of larger volume could be caused simply by an increase in size and density or a redistribution or a decreased amount of anionogenic groups on platelet surface. Reported experiments (Brinton and Lauffer, 1959) make it less likely that the slow mobility is due to the large size. Disappearance of the platelet with large volume and low electrophoretic mobility would be caused by a selective consumption into the thrombi.Summary: 1. Increase in electrophoretic mobility was observed in platelets of the ADP-induced thrombosis. 2. Larger platelets carry low electro-phoretic mobility, 3. Platelets with large volume and low mobility were most likely consumed selectively into the thrombi.