Figure 5

Outward rectifying currents after three days in proliferation medium and further six days in differentiation medium. (A) Original current traces in an extracellular solution containing 1 mM Ba²⁺ to eliminate contributions of inwardly rectifying K⁺ currents from cell cultured under condition d3C. (B) Current to voltage relationship of mean currents shown in (A) measured between 45 and 55 ms between the two vertical dashed lines in (A). (C) All cells recorded from showed delayed rectifier currents (I_KDR) (control: C, pretreatment with TNF-α and IFN-γ for 48 hours:TI, control cultures treated with dexamethasone: CD, cultures co-treated with dexamethasone and TNF-α and IFN-γ for 48 hours: TID, numbers of cells investigated given below bars). Note, that cytokine treatment significantly reduced I_KDR after 3 days in proliferation medium in accordance with [52]. In contrast to control cells, in which a significant down-regulation took place after 6 days in differentiation medium (d3C versus d9C), outward K⁺-currents in cytokine pretreated biopolar cells showed no further down-regulation in differentiation medium (d3TI versus d9TI, p > 0.05). A coincubation with dexamethasone however, led to a signficant downregulation of I_KDR in the surviving multipolar cells (d9TI versus d9TID) resulting in a I_KDR density indiscernable from that recorded in cells differentiated under control conditions (d9TID versus d9C, p > 0.5). Error bars denote mean ± SE. * p < 0.05, ** p < 0.01, *** p < 0.001).