title: Congenital deficiency of alpha-2-adrenoceptors on human platelets: description of two cases.
abstract: The biochemistry and functionality of platelets from two related subjects (mother and son) with alpha-2-adrenoceptor-deficient platelets has been evaluated. Radioligand binding experiments with the specific alpha-2-adrenergic-receptor antagonist, 3H-yohimbine, showed a drastic reduction of alpha-2-adrenoceptors in platelets from both subjects in comparison with the control values. Electron microscopy studies revealed a normal morphology and a normal number of alpha granules and dense bodies. Levels of adenine nucleotides; 5-hydroxytryptamine; B-thromboglobulin; platelet-factor-4 and thromboxane A2 production were within normal limits. Platelet aggregation and 5-hydroxytryptamine production in response to adrenalin (at concentrations up to 50 microM) were absent, whereas ADP, AA, PAF, collagen and thrombin-induced aggregation, secretion, Ca++ flux and thromboxane A2 production were normal. The inhibitory effect caused by different concentrations of prostacyclin on Ca++ flux, aggregation, secretion and thromboxane A2 production of platelet functionally lacking of alpha-2-adrenoceptor was not distinguishable from control platelets and platelets preincubated with yohimbine.
authors.affiliation: Cattedra di Ematologia, Istituto di Medicina Interna, University of Torino, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Tamponi
authors.forename: A
authors.initials: A
authors.lastname: Pannocchia
authors.forename: C
authors.initials: C
authors.lastname: Arduino
authors.forename: M
authors.initials: M
authors.lastname: Bazzan
authors.forename: N
authors.initials: N
authors.lastname: Della Dora
authors.forename: P
authors.initials: P
authors.lastname: Schinco
authors.forename: M
authors.initials: M
authors.lastname: Buraglio
authors.forename: M
authors.initials: M
authors.lastname: Eandi
mesh_terms: D000328:Adult; D001791:Blood Platelet Disorders / Q000097:blood / Q000151:congenital* / Q000235:genetics; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D002648:Child; D004837:Epinephrine / Q000494:pharmacology; D011464:Epoprostenol / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D011464:Epoprostenol; D002118:Calcium; D004837:Epinephrine