Summary
The initial shape change and subsequent aggregation of platelets in citrated rabbit
platelet-rich plasma caused by ADP in vitro was inhibited by 15-hydroxyprostaglandin
dehydrogenase. This inhibition was NAD-dependent and was also seen when shape change
and aggregation were initiated by sodium arachidonate or by collagen. The aggregation
of gel-filtered rabbit platelets by thrombin was not, however, affected by removal
of 15-hydroxyprostaglandins.
Indomethacin was found to inhibit ADP-induced aggregation but at a concentration (250
μM) much higher than that required to inhibit collagen-induced aggregation. Moreover
the platelet release reaction had not taken place 3 min after ADP stimulation. The
direct role 15-hydroxyprostaglandin production in ADP-induced aggregation of rabbit
platelets is proposed. The involvement of 15-hydroxyprostaglandins in platelet aggregation
caused by other inducers is also discussed.