Prostaglandin I2 half-life regulated by high density lipoprotein is decreased in acute myocardial infarction and unstable angina pectoris.

To investigate the prostaglandin I2 (PGI2) half-life regulated by high density lipoprotein (HDL) in patients with coronary artery disease (CAD), we determined the stability of PGI2 and serum apolipoprotein A-I (Apo A-I) and apolipoprotein A-II (Apo A-II) levels in four age-matched groups of patients: controls (n = 17), angina pectoris (n = 18), unstable angina pectoris (n = 17), myocardial infarction (n = 19) (acute phase, 3.6 +/- 1.7 hours from onset; subacute phase, 75 +/- 15 hours from onset in the same patients). Serum PGI2 half-life and total serum Apo A-I levels were lower in the CAD group than in the control group. PGI2 was least stable in patients with unstable angina and the acute phase of myocardial infarction. In these patients, the molar ratio of Apo A-I to Apo A-II and HDL-associated Apo A-I levels were decreased, and free Apo A-I levels were increased. After in vitro incubation of HDL with increasing amounts of Apo A-II, Apo A-I in HDL was displaced by Apo A-II, with the parallel decrease in stability of PGI2. Free Apo A-I cannot stabilize PGI2. HDL-associated Apo A-I, whose amount is affected by Apo A-II, stabilized PGI2 and correlated well with stability of PGI2 in patients with CAD and control patients. Decreased PGI2 half-life may play an important role in the pathogenesis of atherosclerosis and thrombus formation in the coronary arteries, especially thrombus formation during an acute coronary event.