EFFECTS OF GLAUCOCALYXIN-A ON AGGREGATION AND CAMP LEVELS OF RABBIT PLATELETS IN-VITRO

Glaucocalyxin A (Gla A) is a new diterpenoid isolated from ethereal ex tract of the leaves of Rabdosia japonica (Burm f ) Hara ar glaucocalyx (Maxim) Hara (Labiatae) collected in Northeastern China. When incubat ed with washed rabbit platelets, Gla A inhibited ADP-, AA-, and PAF-in duced aggregation of rabbit platelets with IC50 values of 3. 44, 13.32 , and 7.74 mumol . L-1, respectively. Gla A 10 and 100 mumol . L-1 inc reased the cAMP levels in platelets. In combination with imazodan hydr ochloride, Gla A (1 - 100 mumol . L-1) caused a marked increase of pla telet cAMP levels, while no effect with PGE1.