Effects of Aspirin and Sulfinpyrazone on Thromboxane and Prostacyclin Synthesis in Rabbits

Arachidonic acid (AA) or collagen were infused into rabbits causing intravascular platelet aggregation with thrombocytopenia, hypotension and death. Thromboxane and prostacyclin synthesis were measured by radioimmunoassay of plasma TXB₂ and 6-keto-PCF₁α. The effects of pretreatment with aspirin (ASA) or sulfinpyrazone (SPZ) were assessed.

Death in drug-treated rabbits was always associated with elevations of plasma TXB₂ (1-40 ng/ml) and of 6-keto-PGF₁α (1-20 ng/ml). Collagen produced only small elevations of plasma TXB₂ compared to AA but protection by ASA correlated better with inhibition of TXB₂ and 6-keto-PGF₁α synthesis than with inhibition of aggregation. Low dose ASA produced less inhibition of prostacyclin synthesis than high dose ASA but was less effective in preventing thromboxane synthesis and death.