calcimycin and Myeloproliferative-Disorders

Defects in glycoprotein (GP)IIb-IIIa or in its activation may cause abnormal platelet aggregation and a bleeding diathesis. We report studies in a 67-year-old man with a myeloproliferative disease and markedly abnormal platelet responses. By flow cytometry, platelet binding of two complex-specific anti-GPIIb-IIIa monoclonal antibodies (mAbs), A2A9 and 10E5, was approximately 50% of normal. An enzyme-linked immunosorbent assay (ELISA) using immobilized kistrin showed 18% of normal membrane GPIIb-IIIa complex. By immunoblot analysis, GPIIb and GPIIIa levels in platelet lysates and membranes were near normal. Activation of GPIIb-IIIa, monitored with mAb PAC-1, was markedly decreased (< 20% of normal) in response to ADP, thrombin and platelet-activating factor (PAF); expression of ligand-induced binding sites (LIBS) was < or = 30% of normal. Signal transduction-independent LIBS expression, induced by echistatin, was approximately 60% of normal, suggesting that the integrin present had intact ligand-binding capability. Sequence analysis of GPIIb and GPIIIa cDNA, and platelet mRNA levels for both subunits, were normal. These findings document an acquired combined defect in membrane expression (secondary to a defect in post-translational processing of the complex) and inside-out signalling-dependent activation of the GPIIb-IIIa complex.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenosine Diphosphate; Aged; Antibodies, Monoclonal; Binding Sites; Blood Platelets; Calcimycin; Diglycerides; DNA, Complementary; Enzyme Activators; Flow Cytometry; Humans; Immunoblotting; Intercellular Signaling Peptides and Proteins; Ionophores; Macrophage-1 Antigen; Male; Myeloproliferative Disorders; Neutrophils; Peptides; Platelet Activating Factor; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Polymerase Chain Reaction; Protein Binding; Protein Kinase C; Receptors, Thrombin; RNA, Messenger; Sequence Analysis, DNA; Serotonin; Signal Transduction

Mice inoculated with an artificially constructed retrovirus carrying the middle T gene of polyomavirus develop acute myeloproliferative disease with severe thrombotic and hemorrhagic disorder and impaired platelet function. The megakaryocytic lineage appears to be a target for polyoma-murine leukemia virus infection and middle T gene expression. This newly described disease represents a unique model system for studying disorders of the megakaryocytic lineage.

Topics: Adenosine Triphosphate; Animals; Antigens, Viral, Tumor; Calcimycin; DNA, Recombinant; Leukemia Virus, Murine; Mice; Myeloproliferative Disorders; Platelet Aggregation; Polyomavirus; Thrombocythemia, Essential

The arachidonate metabolism by leukocytes and platelets was studied in 14 patients with myeloproliferative disorders including 7 patients with chronic myeloid leukemia (CML), 5 with polycythemia vera (PV) and 2 with essential thrombocythemia (ET). When the leukocytes were incubated with arachidonate and A23187, leukotriene B4 and hydroxyeicosatetraenoic acids (HETEs) were constantly detected using reversed-phase high-performance liquid chromatography in normal subjects, while selective deficiency of 5-lipoxygenase products (leukotriene B4 and 5-HETE) was found in 4 patients with CML. this novel abnormality of the leukocytes seemed to be derived from the possible deficiency of 5-lipoxygenase in these patients' polymorphonuclear neutrophils (PMNNs). The formation of 15-HETE appeared to be almost normal in all the patients. Platelet 12-lipoxygenase deficiency was detected in 2 patients with PV and 2 with CML in whom one was associated with the deficiency of 5-lipoxygenase products. These bicellular abnormalities of the arachidonate metabolism might contribute to understand dysfunctions of PMNNs and platelets in some patients with myeloproliferative disorders.

Topics: Arachidonate Lipoxygenases; Arachidonic Acid; Arachidonic Acids; Blood Platelets; Calcimycin; Humans; In Vitro Techniques; Leukemia, Myeloid; Leukocytes; Leukotriene B4; Lipoxygenase; Myeloproliferative Disorders; Polycythemia Vera; Prostaglandin-Endoperoxide Synthases; Thrombocytosis

A group of patients with myeloproliferative disorders was studies with respect to platelet aggregation responses, release of beta-thromboglobulin and incorporated 5-hydroxy-tryptamine, and synthesis of thromboxane b 2. In all patients the resting plasma beta-thrombo-globulin was elevated. Aggregation responses were frequently impaired to adrenaline, arachidonic acid, A23187 and the prostaglandin endoperoxide analogue, U44069. Both 5-hydroxy-tryptamine and beta-thromboglobulin release were greater with patients' platelets than with those of controls in response to adrenaline, ADP and U44069. The patients' platelets produced more thromboxane B2 than did controls, irrespective of the agonist used, yet those aggregating agents which are thought to act by generating thromboxane A2 were relatively ineffective in causing aggregation. This might reflect resistance to thromboxane A2 action in these patients, which is met by increased thromboxane formation.

Topics: Adenosine Diphosphate; Adult; Aged; Arachidonic Acid; Arachidonic Acids; beta-Thromboglobulin; Blood Platelets; Calcimycin; Collagen; Epinephrine; Female; Humans; Male; Middle Aged; Myeloproliferative Disorders; Platelet Aggregation; Prostaglandin Endoperoxides, Synthetic; Ristocetin; Serotonin; Thromboxane B2; Thromboxanes