PRE-AGGREGATION REACTIONS OF PLATELETS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 58  (3) , 477-490
Abstract
Whether [human] platelet volume increases during the morphological changes preceding aggregation was investigated. Previous research is controversial; resistive-counting techniques reveal an increase, centrifugal methods do not. Platelets were sized with a computerized, resistive-particle counter before and after incubation with ADP. Resistive volume increased by 14% (P < 0.001) in the absence of EDTA, and only 7% in its presence (ADP, 10 .mu.M). EDTA inhibited platelet volume changes, whether these were shrinking induced by warming or swelling by ADP. Handling of platelets, such as during centrifugation, also caused particle swelling. Particle density decreased after ADP exposure, without release of serotonin, suggesting uptake of water. Platelet shape was experimentally manipulated to test the hypothesis that resistive volume changes stem from artifacts of particle shape. Scanning electron microscopy confirmed that colchicine, chlorpromazine and a temperature cycle of 0.degree.-37.degree. C all caused extensive alteration from the disc shape. Subsequent exposure to ADP increased resistive volume, and in the case of chlorpromazine, no long pseudopodia were extruded. Preaggregation reactions of platelets can be associated with an increase in particle volume. Earlier research based on centrifugation and the presence of EDTA failed to reveal the increase because of inhibitory and apparent swelling effects.