Influence of diamide on aggregation, cytoskeletal proteins and arachidonic acid metabolism in human platelets

Simultaneous addition of diamide (azodicarboxylic acid-bis-dimethylamide, DIA), a SH-oxidizing agent, and collagen causes a deaggregation of otherwise irreversibly aggregating platelets. Thromboxane B2 (TXB2) and 12-HE-TE formation is inhibited depending on the concentration ratio between collagen and DIA. Thus, at 0.25 mM DIA and 20 micrograms/ml collagen neither TXB2 nor 12-HETE were measurable, but a full scale reversible aggregation is induced. Deaggregation is further attained by adding DIA to collagen-induced aggregates at a time, when maximum amplitude has been achieved. Investigation of arachidonic acid (AA) metabolites under these conditions revealed no influence of DIA on AA metabolism. Therefore, AA metabolization seems to play a minor role in collagen-induced aggregation and DIA-induced deaggregation. Polymerization of certain cytoskeletal proteins of the platelets, after addition of DIA, parallels DIA-induced deaggregation. DIA inhibits endogenous AA release, probably by interaction with platelet plasma membrane. DIA seems to inhibit the release of the alpha-granula protein thrombospondin