Figure 4. I_f is normal, but I_CaL is diminished in KI SAN cells.

(A) Left, family traces of I_f in a WT (top) and RyR₂^R420Q (middle) cell, with the voltage protocol below. Right, I_f current density–voltage relationship in 8 WT cells (open black circles) and 8 KI cells (gray squares). (B) I_CaL peak current density is unchanged recorded at –10 mV with a 10 mM BAPTA Ca²⁺ buffered intracellular solution, in 12 WT and 15 KI SAN cells. Sample traces at –10 mV and voltage protocol are shown on top. Bar graphs display I_CaL averaged current densities (current amplitude divided by the cell capacitance) expressed as the mean ± SEM (white for WT and gray for KI) with individual data shown on the columns. (C) I_CaL current is decreased at –10 mV in Ca²⁺ unbuffered intracellular solution. Same conditions as in B, but without intracellular BAPTA, n = 16 WT and 11 KI cells. *P < 0.05 by t test.