Abstract: AIM:To study the expression and electrophysiological characteristics of MaxiK channels in the process of human macrophage development and differentiation to foam cells. METHODS: Monocyte-derived macrophages were isolated from human peripheral blood. The mRNA level and MaxiK channel expression were detected using real time RT-PCR and Western blot technique and the whole cell MaxiK current from macrophages was measured using patch clamp technique. RESULTS: In the development of macrophage cells, the expression of MaxiK channel was slightly upregulated. Compared with those in the 5-day group, mRNA and protein expression in the 7.5-day group increased 1.06 and 1.44 times, respectively. However, 30 mg/L oxLDL significantly increased the mRNA expression of MaxiK. After differentiating into foam cells, MaxiK mRNA and protein expression were 2.4 and 7.27 times higher than those in the 5-day group (P<0.05). The MaxiK current was obtained from 5 day, 7.5 day and oxLDL groups. Paxilline (10 μmol/L), the selective blocker of MaxiK, inhibited the time-dependent current and abolished the outward conductance and noises. In 5-day, 7.5-day and oxLDL groups, the MaxiK current densities were (36±6) pA/pF, (35.9±3.5) pA/pF and (32.4±6.9) pA/pF respectively, Which did not show a significant difference. CONCLUSION: In the development of human macrophages, expression of MaxiK channel is upregulated. Upregulation is more obvious after its differentiation into foam cells. However, the MaxiK current remains unchanged during development and differentiation.