Role of cyclic nucleotides in rapid platelet adhesion to collagen.
Adhesion of human platelets to type I collagen under arterial flow conditions is extremely fast, being mediated primarily by the alpha 2 beta 1 integrin (glycoprotein Ia/IIa). We have investigated the involvement of cyclic nucleotides in platelet adhesion to soluble native collagen immobilized on Sepharose beads using a new microadhesion assay under arterial flow conditions. To prevent platelet stimulation by thromboxanes and adenosine diphosphate (ADP), experiments were performed with aspirin-treated platelets in the presence of ADP-removing enzyme systems such as creatine phosphate/creatine phosphokinase or apyrase. Rapid reciprocal changes in platelet adenosine 3'5'-cyclic monophosphate (cAMP) and guanosine 3'5'-cyclic monophosphate (cGMP) occurred during adhesion. cAMP levels in adherent platelets were 2.4-fold lower than in effluent platelets or in static controls, whereas cGMP levels were increased 2.4-fold. These results suggest that contact between platelets and collagen stimulates guanylate cyclase and inhibits adenylate cyclase. This occurs in the absence of the platelet release reaction. We also studied short-term effects of agents that regulate cyclic nucleotide synthesis, prostaglandin E1 (PGE1) and sodium nitroprusside (SNP). After only 3.8 seconds at 10 to 30 dyne/cm2, PGE1 (10 mumol/L) increased cAMP 16.4-fold, whereas SNP (50 mumol/L) increased cGMP ninefold and caused a 3.2-fold increase in cAMP. Both PGE1 and SNP rapidly (< 5 seconds) inhibited platelet adhesion in a dose-dependent manner that was correlated with the increase in cyclic nucleotides. Our data suggest that cAMP and cGMP play a regulatory role in the initial phases of platelet adhesion to collagen mediated by the alpha 2 beta 1 integrin receptor.
Polanowska-Grabowska
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Department of Biochemistry, University of Virginia, School of Medicine, Charlottesville 22908.
Gear
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D000262:Adenylyl Cyclases / Q000097:blood; D000527:Alprostadil / Q000494:pharmacology; D015703:Antigens, CD / Q000502:physiology; D001081:Apyrase / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000502:physiology; D003094:Collagen / Q000378:metabolism*; D003402:Creatine Kinase / Q000494:pharmacology; D000242:Cyclic AMP / Q000097:blood*; D006152:Cyclic GMP / Q000097:blood*; D006162:Guanylate Cyclase / Q000097:blood; D006801:Humans; D019012:Integrin beta1; D016023:Integrins / Q000502:physiology; D009599:Nitroprusside / Q000494:pharmacology; D010973:Platelet Adhesiveness / Q000502:physiology*
D015703:Antigens, CD; D019012:Integrin beta1; D016023:Integrins; D009599:Nitroprusside; D003094:Collagen; D000242:Cyclic AMP; D003402:Creatine Kinase; D001081:Apyrase; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D000527:Alprostadil; D006152:Cyclic GMP; D001241:Aspirin