Objective: To investigate the effect of acute mixed hyperlipidemia on acute myocardial infarct size and the potential mechanism.
Methods: 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.
Results: 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).
Conclusion: Acute mixed hyperlipidemia could increase acute myocardial infarct size. The role of lipoprotein j associated phospho-lipase A(2) in it was not clear.