AICAR-induced I_HCN4 inhibition in HEK293T vs HEK293F cells. Fully activated I_HCN4 I/V curves normalized to capacitance measured from hHCN4-transfected HEK293T (left) or HEK293F cells (right) under control conditions (black) and following 4-h incubation in AICAR-containing solution (1 mM) (red). Linear fitting led to normalized conductance values of 0.704 (n = 16) and 0.418 nS/pF (n = 13) for HEK293T and 1.035 (n = 20) and 0.501 nS/pF (n = 23) for HEK293F cells, in control conditions and following AICAR incubation, respectively. The current density reduction due to AICAR treatment was thus 40.6% in HEK293T and 51.6% in HEK293F cells.