Aim To study the differential effects of human very low density lipoprotein (VLDL) subfractions with different apolipoprotein E content on the expression of apolipoprotein E gene in mouse peritoneal macrophages (MPMs). Methods Apolipoprotein E-rich and apolipoprotein E -poor subfractions of normal human VLDL with different apolipoprotein E content were separated by Heparin-sepharose CL-6B affinity chromatography and incubated with MPMs at different concentrations respectively. Their effects on the expression of MPM apolipoprotein E gene were determined at both mRNA and protein level with Northern blotting essay and SDS-polyacrylamide gel electrophoresis respectively. Results At concentration of triglyceride 100 μg /L medium, both apolipoprotein E-rich and apolipoprotein E-poor subfractions could stimulate expression and secretion of apolipoprotein E in MPMs, with apolipoprotein E-poor subfraction demonstrating more potent:a nearly two-fold increase in the mRNA and protein level (1.58 and 1.82-fold respectively) was observed in the cells treated with apolipoprotein E-poor subfraction compared to the slight increase in cells treated with its apolipoprotein E-rich counterpart (1.10 and 1.25-fold respectively). However, the case was quite different for cells treated with that two subfractions at 1 000 μg/L of triglyceride medium. The mRNA level was similarly inhibited to a level of 65% of control cells in contrast to elevated apolipoprotein E protein level at more than two-fold. However, the reasons remain obscure at present. Conclusion These findings might suggest that apolipoprotein E -poor VLDL has higher potentiality to stimulate the expression of apolipoprotein E at only relatively low concentration, but does not at high concentration level. 还原