A comparative review on heart ion channels, action potentials and electrocardiogram in rodents and human: extrapolation of experimental insights to clinic

Table 2 Main ionic currents and their proteins, gens and densiti in cardiac atrium 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, 48]
1	Ito,f (outward)	Kv4.2 Kv4.3	KCND2 KCND3	+++	+	–	+++	+++ [7, 31, 45, 46, 48]
1	Ito,s (outward)	Kv1.4	KCNA4	+++	+++	–	+++	+++ [7, 31, 45,46,47,48]
1	IKur (outward)	Kv2.1 Kv1.5	(KCNB1) (KCNA5)	++	++	+	++	++ [7, 31, 46]
2	ICaL (inward)	Cav 1.2	CACNA1C	++	++	++	++	++ [7, 31, 45, 47, 48]
2, 3	IKr (outward)	Kv11.1	KCNH2 (HERG)	+	+	+	+	+ [7, 19, 31, 45,46,47,48]
2, 3	IKs (outward)	Kv7.1 (KvLQT1)	KCNQ1	+	+	++	+	+ [7, 19, 31, 45,46,47,48]
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	Atrial-specific 4-aminopyridine-sensitive (outward)	Kv1.5	KCNA5	++	?	?	++	++ [7, 31, 45]
3 and 4 RMP	IK1 (outward)	Kir2.1/Kir2.2	KCNJ2	+	+	+	+	+ [7, 31, 45, 47, 48]
2	INCX	NCX1, NCX2	SLC8A1	+	+	+	+	+ [7, 47]

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; IK1, inward rectifier potassium current; INCX, Na⁺–Ca²⁺ exchanger current; RMP, resting membrane potential; – (no existing); + (the existing rate); ?: indistinctive

ISSN: 2233-7660