15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and Blood-Platelet-Disorders

Chronic hemorrhagic diathesis in patients showing normal levels of plasmatic clotting factors strongly suggests for congenital platelet disorders. We report on a pediatric patient (male, 3 years, D1) with mild bleeding. A sibling (D2), his mother (D3) and father (D4) were included for laboratory investigation. Platelet counts in D1, D2 and D4 indicated mild thrombocytopenia (100 Gpt/L). D1 and D3 platelets showed significantly diminished aggregation response on arachidonic acid and U46619 stimulation. Immunostaining for platelet proteins on blood smears of D1 and D2 indicated defects in ß1-tubulin. Exon sequencing of

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adult; Arachidonic Acid; Blood Platelet Disorders; Blood Platelets; Child, Preschool; Female; Hemorrhage; Hemorrhagic Disorders; Heterozygote; Humans; Male; Mutation; Phenotype; Platelet Count; Receptors, Thromboxane A2, Prostaglandin H2; Thrombocytopenia; Tubulin

Light transmission aggregometry (LTA) is commonly performed to assess individuals for bleeding disorders.. The goal was to evaluate the incidence and spectrum of platelet function abnormalities in a prospective cohort of individuals referred for bleeding disorder assessments after exclusion of thrombocytopenia and von Willebrand disease.. Subjects were healthy controls and patients from a prospective cohort of individuals referred for bleeding disorder assessments after exclusion of thrombocytopenia and von Willebrand disease. LTA was performed by standardized methods using platelet-rich plasma adjusted to 250x10(9) platelets L(-1). Maximal aggregation data were analyzed to determine the likelihood of detecting a platelet function disorder by LTA, and the sensitivity and specificity of LTA for platelet disorders.. The incidence of false positive LTA among subjects excluded of having bleeding disorders was similar to healthy controls. Abnormal LTA was more common in subjects with bleeding disorders and the likelihood of a bleeding disorder was significantly increased (odds ratio 32) when maximal aggregation was reduced with two or more agonists. Receiver operator curve analyses indicated that LTA had high specificity and moderate sensitivity for detecting inherited defects in platelet function and that the LTA agonists 1.25 microg mL(-1) collagen, 6 microM epinephrine, 1.6 mM arachidonic acid and 1.0 microM thromboxane analogue U44619 detected most inherited disorders with abnormal LTA.. LTA is valuable for detecting platelet function abnormalities among individuals referred for bleeding problems, particularly when the test indicates abnormal responses to multiple agonists.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Arachidonic Acid; Blood Platelet Disorders; Case-Control Studies; Collagen; Epinephrine; False Positive Reactions; Humans; Nephelometry and Turbidimetry; Platelet Aggregation; Platelet Function Tests; Prospective Studies; ROC Curve; Sensitivity and Specificity

We describe an 11-year-old girl with a mild bleeding disorder since early childhood. The disorder was characterized by a prolonged bleeding time, and the patient's platelets showed defective aggregation responses to thromboxane A2 (TXA2) mimetic U46619 and arachidonic acid. In contrast, the platelets showed normal responses to thrombin and Ca ionophore A23187. When the platelet TXA2 receptor was examined with the [3H]-labeled TXA2 agonist U46619, the equilibrium dissociation rate constants (kd) and the maximal concentration of binding sites (Bmax) of the patient's platelets were within normal ranges. Normal GTPase activity was also induced in the patient's platelets by stimulation with U46619, however, inositol 1,4,5-triphosphate (IP3) formation was not induced by U46619. These results suggests that the patient's platelets had a defect in phospholipase C activation beyond TXA2 receptors.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenosine Diphosphate; Blood Platelet Disorders; Blood Platelets; Calcimycin; Child; Female; GTP Phosphohydrolases; GTP-Binding Proteins; Humans; In Vitro Techniques; Inositol 1,4,5-Trisphosphate; Kinetics; Platelet Aggregation; Prostaglandin Endoperoxides, Synthetic; Receptors, Thromboxane; Signal Transduction; Thrombin; Thromboxane A2; Type C Phospholipases

A four-year-old Standardbred gelding presented with a 3.5 year history of intermittent epistaxis and spontaneous submucosal petechiae and ecchymoses in the nares and the mouth. Routine haematological and biochemical examinations were unremarkable. A thrombocytopathy was suspected when activated partial thromboplastin time, one stage prothrombin time, plasma fibrinogen and the platelet count were all normal. The patient's platelets failed to aggregate with serotonin, adenosine diphosphate, collagen (at 20 micrograms/ml) or the endoperoxide analogue U46619. Very high levels of collagen (100 micrograms/ml) did cause aggregation. The response to the calcium ionophore A23187 was reduced and although complete degranulation occurred the resulting aggregates were unstable. Thromboxane generation in response to collagen and ADP was inferred from the concentration of its stable metabolite thromboxane B2 and was reduced. A diagnosis of a thrombasthenia-like syndrome possibly equivalent to Type II Glanzmann's thrombasthenia in people was made.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenosine Diphosphate; Animals; Blood Platelet Disorders; Blood Platelets; Calcimycin; Collagen; Epistaxis; Female; Horse Diseases; Horses; Male; Microscopy, Electron; Platelet Aggregation; Prostaglandin Endoperoxides, Synthetic; Serotonin; Thrombasthenia

To determine the pathogenetic mechanism of a hereditary primary platelet release disorder, arachidonic acid metabolism via the cyclooxygenase pathway was investigated. The propositus' platelets exhibited defective release reaction and second-wave aggregation when stimulated by sodium arachidonate or U46619, a thromboxane A2 (TXA2) agonist. The lack of platelet response to U46619 suggested that the defect was beyond the thromboxane synthetase level. Furthermore, thromboxane B2 (TXB2) formation in the propositus' platelets (558.52 ng/10(8) platelets) was within the normal range (574.29 +/- SD 27.39 ng/10(8) platelets) and TXA2 formation appeared to be adequate for aggregating normal platelets. The results were indicative of an abnormal platelet response to TXA2. Failure of the propositus' platelets to aggregate in response to TXA2 formed in normal platelet-rich plasma induced by arachidonate confirmed this notion. To gain further insight, platelet cyclic (c) AMP content was determined. Prostacyclin induced a significant elevation of the propositus' platelet cAMP level comparable to normal values. U46619 suppressed prostaglandin I2-induced cAMP elevation in normal subjects but had no such effect in the patient. We conclude that the primary release disorder observed in this kindred is due to an abnormal platelet respnse to TXA2 possibly because of TXA2/PGH2 receptor abnormalities.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adult; Arachidonic Acids; Blood Platelet Disorders; Blood Platelets; Cyclic AMP; Epoprostenol; Female; Humans; Platelet Aggregation; Prostaglandin Endoperoxides, Synthetic; Thromboxane A2; Thromboxanes