Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

Abstract

The authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼⁵ molar, 121.8 ± 7.8% by 3 × 10^-6 molar and 129.4 ± 12.8% of the value before the injection by 10”⁶ molar ADP. The difference was statistically significant (P-5 or 3 × 10^-6 molar and 129.4 ± 12.8% of the value before 10∼⁶ molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.