Role of autocrine stimulation for the effects of cyclic AMP on protein and lipid phosphorylation in platelets activated by particles.
We have compared responses in platelets stimulated with the particulate materials, Intralipid (liposome-suspension) and a potential contrast medium IEEC (1'-(ethyloxycarbonyloxy)-ethyl-5-acetyl-amino-3-(N-methyl-acetyla mino)-2,4,6-triiodo-benzenecarboxylate coated with human serum albumin), with and without forskolin and inhibitors of autocrine stimulation (IAS: an ADP-removing system of creatine phosphate/creatine phosphokinase; RGDS to prevent fibrinogen/fibronectin binding to GPIIb/IIIa; SQ 29.548 as a TXA2 receptor antagonist; cyproheptadine as a serotonin receptor antagonist; BN 52021 as a platelet-activating factor receptor antagonist). The pattern of tyrosine-phosphorylated proteins, phosphorylation of initial lipids and phosphorylation of pleckstrin (P47) were used as markers for early signal transducing responses, while secretion of ADP+ATP and beta-N-acetyl-glycosaminidase were used as final responses. Intralipid showed no platelet activation except for some weak tyrosine protein phosphorylation that was inhibited by elevated cAMP. IEEC induced strong platelet activation that was partly inhibited by increased levels of cAMP and IAS. The inhibition of elevated cAMP seemed to be due to removal of the G protein-mediated activation from secreted autocrine stimulators either by IAS or forskolin. The remaining activity is a pure effect from IEEC which is not affected by elevated cAMP.
Ryningen
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Department of Biochemistry and Molecular Biology, University of Bergen, Norway. anita.ryningen@pki.uib.no
Holmsen
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H
D000244:Adenosine Diphosphate / Q000097:blood; D000255:Adenosine Triphosphate / Q000097:blood; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology*; D003287:Contrast Media / Q000494:pharmacology; D000242:Cyclic AMP / Q000097:blood*; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism; D005217:Fat Emulsions, Intravenous / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008055:Lipids / Q000097:blood*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008794:Metrizoic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D010710:Phosphates / Q000097:blood; D010743:Phospholipids / Q000097:blood; D010750:Phosphoproteins; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000097:blood; D015539:Platelet Activation / Q000187:drug effects; D011493:Protein Kinase C / Q000097:blood; D012709:Serum Albumin
C081963:(1'-ethyloxycarbonyloxy)ethyl 5-acetylamino-3-(N-methylacetylamino)-2,4,6-triiodobenzenecarboxylate; D001798:Blood Proteins; D003287:Contrast Media; D005217:Fat Emulsions, Intravenous; D008055:Lipids; D010710:Phosphates; D010743:Phospholipids; D010750:Phosphoproteins; D012709:Serum Albumin; C039077:platelet protein P47; D005576:Colforsin; D019000:Phosphotyrosine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D008794:Metrizoic Acid; D000242:Cyclic AMP; D011493:Protein Kinase C