TABLE 1

Sensitivity to ATP of native and recombinant channels

Channel, condition	Configuration	IC₅₀ (μmol/l)	h	n
Native, +Mg²⁺	Open-cell	156 ± 40*	1.1 ± 0.2	10
	Inside-out	22 ± 2	1.5 ± 0.1	5
Native, Mg²⁺ free	Open-cell	15 ± 4.0 (NS)	1.6 ± 0.2	10
	Inside-out	9.6 ± 0.8	1.0 ± 0.2	5
Kir6.2/SUR1, +Mg²⁺	Open-cell	371 ± 27†	1.0 ± 0.1	6
	Inside-out	36 ± 8§	0.9 ± 0.1	7
Kir6.2/SUR1, Mg²⁺ free	Open-cell	47 ± 3§	1.1 ± 0.1	4
Kir6.2/SUR1-KAKM, +Mg²⁺	Open-cell	73 ± 14‡	0.9 ± 0.1	4
	Inside-out	31 ± 6	1.2 ± 0.2	7
Kir6.2/SUR1-KAKM, Mg²⁺ free	Open-cell	43 ± 10§	1.1 ± 0.1	4

Data are means ± SE. Results from native K_ATP channels (in β-cells) or recombinant K_ATP channels expressed in HEK cells (Kir6.2/SUR1; Kir6.2/SUR1-KAKM). Mg²⁺ was present in the internal solution as indicated.
* P < 0.005;
† P < 0.01;
‡ P < 0.05; NS, nonsignificant, when compared with equivalent data in the inside-out patch configuration.
§ Nonsignificant compared with open-cell data in Mg²⁺-containing solution for Kir6.2/SUR1-KAKM. h, Hill coefficient; n, number of patches.