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EFFECTS OF CONCANAVALIN A ON 5‐HYDROXYTRYPTAMINE UPTAKE BY RABBIT BLOOD PLATELETS AND ON THEIR ULTRASTRUCTURE
Author(s) -
NISHIO H.,
SEGAWA T.,
TAKAGI H.
Publication year - 1979
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1979.tb07864.x
Subject(s) - platelet , concanavalin a , wheat germ agglutinin , theophylline , agglutinin , colchicine , ultrastructure , biochemistry , chemistry , cytochalasin b , lectin , medicine , guanosine , endocrinology , biology , anatomy , cell , in vitro
1 Effects of concanavalin A (Con A) and other lectins on 5‐hydroxytryptamine (5‐HT) uptake by rabbit blood platelets and on their ultrastructure were studied. 2 Uptake of [ 3 H]‐5‐HT by platelets was decreased by application of Con A, E‐PHA (lectin from Phaseolus vulgaris) and lentil‐PHA (lectin from Lens culinaris) , but not by wheat germ agglutinin (WGA). Con A induced specific changes in the ultrastructure of platelets, causing (i) a change in external appearance from a discoid to an irregularly spherical shape, (ii) re‐arrangement of the canalicular system and formation of a concentric structure. These effects of Con A on platelets were antagonized by pretreatment with α‐methyl‐D‐mannoside (a‐MM), a specific inhibitor of Con A binding to glycoprotein. 3 The inhibition of 5‐HT uptake by Con A was antagonized by colchicine, vinblastine and sodium nitroprusside (SNP), but not by cytochalasin B. 4 Theophylline, papaverine and dibutyryl cyclic adenosine 3′,5′‐monophosphate (db cyclic AMP) antagonized the effect of Con A on 5‐HT uptake, but dibutyryl cyclic guanosine 3′,5′‐monophosphate had no effect. Theophylline and db cyclic AMP did not influence the effect of Con A on the ultrastructure of platelets. 5 It is suggested that binding of Con A to specific receptor glycoproteins can inhibit the 5‐HT uptake system of platelets. Microtubules, contractile protein and the membrane adenylate cyclase system of platelets may also be regulatory factors in this mechanism.