GRAY PLATELET SYNDROME - ALPHA-GRANULE DEFICIENCY - ITS INFLUENCE ON PLATELET-FUNCTION

  • 1 January 1981
    • journal article
    • research article
    • Vol. 98  (6) , 831-848
Abstract
The ultrastructure, cytochemistry, biochemistry and functions of platelets from 2 patients with the familial gray platelet syndrome are described. Ultrastructural studies showed a lack of .alpha.-granules in the megakaryocytes in the vicinity of a marrow myelofibrosis and/or in platelets. A normal number of mitochondria and a slight increase of dense bodies was confirmed by labeling the whole platelet with mepacrine. Platelet peroxidase (in the dense tubular system) and catalase-positive granules (revealed by the cytochemistry) were present. Platelets from both patients had severe deficiency of .beta.TG [.beta.-thromboglobulin] either after tritonization (< 4% of normal) or thrombin treatment (< 15% of normal) and the plasma .beta.TG levels were slightly increased. Functional studies of these platelets showed an uptake of [14C]5HT [5-hydroxytryptamine] inhibited by reserpine similar to that in the control platelets. Thromboxane formation was within normal limits in the presence of arachidonic acid, ADP, collagen or ionophore A23187 [calcimycin], indicating that the cyclooxygenase/thromboxane synthetase systems were not altered and the phospholipase activities were not impaired. Although the platelet adhesion to prepolymerized fibrillar type III collagen and the ADP-, arachidonic acid- and ionophore A23187-mediated aggregations were apparently normal, in every case the release of [14C]5HT was either at the low side of the normal range or decreased. This abnormality was increased when collagen or thrombin was added to either PRP [platelet-rich plasma] or washed platelets from both patients, where at the same time, the aggregation and the release were markedly reduced. Apparently .alpha.-granules or their content has an influence on the platelet aggregation and dense bodies involved in the [14C]5HT release reaction.