Release of adenine nucleotides and platelet factor 4 from platelets of man and four other species.

Abstract

Abstract Release of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and platelet factor 4 (PF 4 ) from the blood platelets of man, rabbit, pig, cat, and guinea pig was studied in response to various platelet-aggregating agents. Platelet-rich citrated plasma from man, guinea pig, and the cat showed 2 phases of aggregation in response to ADP and thrombin, as measured by a turbidimetric technique. During the second phase of aggregation, but not the first, increasing amounts of platelet ADP were released. In man and the cat, PF 4 was also released during the second phase of aggregation. Platelet-rich citrated plasma from rabbits and pigs did not show a second phase of aggregation, nor was platelet ATP, ADP, or PF 4 released in significant amounts. However, washed pig and rabbit platelets readily released their ATP, ADP, and PF 4 in response to thrombin. Among the species studied, human platelets are especially responsive to epinephrine in vitro, and the release reaction is more readily induced than in the other species. The similarity in behavior of cat, guinea pig, and human platelets suggests that cats and guinea pigs may be more suitable animals for the study of platelet thrombosis than either pigs or rabbits.