[Effects of acute mixed hyperlipidemia on acute myocardial infarction size and its mechanism]

To investigate the effect of acute mixed hyperlipidemia on acute myocardial infarct size and the potential mechanism.

Fifty-three Sprague-Dawley (SD) rats were divided into three groups: the control group (n=15) was injected with 1.0 mL 0.9% sodium chloride, the low dose group (n=17) and high dose group (n=21) were injected with 0.5 mL and 1.0 mL 10% Triton WR-1339 solution respectively. Acute myocardial infarction was produced 24 hours after the injection. Serum lipid and the activity of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) were measured before and 24 hours after the injection. Rats were killed 24 hours after ligation and their hearts were excised to evaluate the myocardial infarct size.

Serum total cholesterol (TC) and triglycerides (TG) concentrations were (6.92+/-1.48) mmol/L and (11.76+/-2.76) mmol/L in the low dose group 24 hours after injection, (11.91+/-0.87) mmol/L and (33.97+/-5.85) mmol/L in the high dose group, and both increased significantly compared with the baseline. Also serum low density lipoprotein cholesterol (LDL-C) concentration increased (P<0.05) in the two groups, but high density lipoprotein cholesterol (HDL-C) had an obvious decrease (P<0.01). And 24 hours after injection, the activity of Lp-PLA(2) in the control group, low dose group and high dose group did not differ compared either with the baseline or among them (P>0.05). Myocardial infarct size was significantly (P<0.001) larger in the low dose group compared with the control group [(55.2+/-3.1)% vs (37.0+/-4.2)%, respectively, P<0.001], so was in the high dose group [(51.4+/-8.3)% vs (37.0+/-4.2)%, respectively, P<0.001], but it did not differ between the two groups(P=0.31).

Acute mixed hyperlipidemia could increase acute myocardial infarct size. The role of lipoprotein j associated phospho-lipase A(2) in it was not clear.