A comparative study of collagen induced thromboxane release from platelets of different species: implications for human atherosclerosis models.

The role of thromboxane in human, rabbit, dog, pig and sheep platelet aggregation has been studied. Each of these species showed a concentration-dependent relationship between collagen concentrations and the thromboxane B2 (TXB2) released from aggregating platelets, however sheep platelets produced only 17.5% of the amount of TXB2 released from human platelets under the same collagen stimulus. Indomethacin did not inhibit sheep platelet aggregation in the concentration range 0.114 mM - 0.114 muM, yet proved to be a potent inhibitor of human platelet aggregation. The prostaglandin endoperoxide analogue, U.46619, induced human platelet aggregation at a dose of 100 ng, however the analogue, at doses as high as 500 micrograms was much less active on sheep platelets when compared to human platelets. Thus we have demonstrated that there are differences in the extent of thromboxane involvement in platelet aggregation between different species, which must be considered with other criteria, before choosing an animal model for studying human atherosclerosis.