Table 3.

Main ionic currents and their proteins, gens and density in cardiac ventricle of human and small animals mediating excitable activity

Action potential phase	Current/transporter	Protein (α sub unit)	Gen
0	INa (inward)	Nav1.5	SCN5A	+++	+++	+++	++++	++++[7, 19, 31, 47–49]
1	Ito,f (outward)	Kv4.2 Kv4.3	KCND2 KCND3	++	+	–	+++	+++ [7, 31, 45, 46, 48]
1	Ito,s (outward)	Kv1.4	KCNA4	++	+	–	++	++ [7, 31, 45–49]
1	IKur (outward)	Kv2.1 Kv1.5	(KCNB1) (KCNA5)	–	+	–	++	++ [7, 31, 46, 49]
2	ICaL (inward)	Cav 1.2	CACNA1C	+++	+++	+++	++	++ [7, 31, 45, 47–49]
2, 3	IKr (outward)	Kv11.1	KCNH2 (HERG)	+++	+++	+++	+	+ [7, 19, 31, 45–49]
2, 3	IKs (outward)	Kv7.1 (KvLQT1)	KCNQ1	+++	+++	++++	+	+ [7, 19, 31, 45–49]
3	IK,slow1 (outward)	Kv1.5	KCNA5	–	–	–	++	++ [7, 31, 45, 47, 48]
3	IK,slow2 (outward)	Kv2.1	KCNB1	–	–	–	++	++ [7, 31, 45, 48]
3	Iss (outward)	Kv1.5	KCNA5	–	–	–	+	++ [7, 31, 48]
3 and 4 (RMP)	IK1 (outward)	Kir2.1/Kir2.2	KCNJ2	++	++	++	++	++ [7, 31, 45, 47–49]
2	INCX	NCX1, NCX2	SLC8A1	++	++	++	++	++ [7, 47, 49]

INa, fast Na current; IKur, ultra-rapid outward K current; Ito,f, fast transient outward K current; Ito,s, slow transient outward K⁺ current; ICaL, L-type Ca current; IKr, rapid delayed rectifier K current; IKs, slow delayed rectifier K current; IK,slow1, 4-aminopyridine-sensitiverapidly activating slowly inactivating K current1; IK,slow2, 4-aminopyridine-sensitiverapidly activating slowly inactivating K current2; Iss, sustained 4-aminopyridinesensitive delayed rectifier K current; INCX, Na⁺–Ca²⁺ exchanger current; RMP, resting membrane potential; – (no existing); + (the existing rate)