Inhibition of thromboxane A2 synthesis in rats treated with phenobarbital

The effect of phenobarbital administration on serum lipoproteins and thromboxane A2 synthesis in platelets was studied in rats. Phenobarbital decreased the serum LDL level by 33% and increased the HDL level by more than 15%. The synthesis of thromboxane A2 in the platelets of the phenobarbital treated animals was found to be reduced by 43%. Thromboxane A2 synthesis in the platelets of the control animals was inhibited by HDL and stimulated by LDL. Hence it appears that the decreased thromboxane A2 synthesis in the platelets of phenobarbital treated rats was at least partly due to the increased HDL and decreased LDL in the serum. Phenobarbital treatment also caused a 15% increase in the serum HDL-cholesterol although it did not have any significant effect on the total serum cholesterol.