Thromboxane B2 biosynthesis and phospholipids hydrolysis in platelets from hypercholesterolemic rabbits.

Thromboxane B2 biosynthesis from arachidonic acid was increased in platelets from hypercholesterolemic rabbits. The enzymic activity of phospholipase A2 which releases arachidonic acid, the precursor for the biosynthesis of thromboxane B2, showed hardly any change in hypercholesterolemic platelets. Phospholipase C and diglyceride lipase activities also were not changed in platelets from hypercholesterolemic rabbits. Furthermore, phospholipid concentration in platelets were not increased in this state. Thus, we conclude that the supply of precursor for thromboxane B2 biosynthesis was not increased in platelets from hypercholesterolemic rabbits as compared to controls. These results suggest that the enzyme activity of thromboxane B2 biosynthesis may be enhanced in platelets from hypercholesterolemic rabbits.