TABLE I A Summary of the Hill Fit... | Rockefeller University Press

TABLE I

A Summary of the Hill Fit Parameters for Luminal Mg²⁺ Inhibition of Cardiac RYRs

No.		[Ca²⁺]_L mM	[Ca²⁺]_C μM	V mV	K_i μM	n_i	P_max, F_max, and τ_max	n	Figure
1	P_o	0.1	0.1	−40	45 ± 5	1.8 ± 0.8	0.33 ± 0.07	17	3 A, 4 A
2	P_o	1.0	0.1	−40	800 ± 180	1.5 ± 1.3	0.071 ± 0.020	11	3 A, 4 A
3	F_o	0.1	0.1	−40	76 ± 27	1.3 ± 1.0	8.8 ± 1.1	6	3 B, 4 B, 6 A
4	F_o	1.0	0.1	−40	876 ± 224	1.3 ± 1.0	11.8 ± 0.9	9	3 B, 4 B
5	τ_o	0.1	0.1	−40	123 ± 23	1.9 ± 1.6	10.0 ± 3.4	6	3 C, 4 C, 6 B
6	τ_o	1.0	0.1	−40	1,000 ± 330	2^{^a}	9.4 ± 5.0	9	3 C, 4 C
7	P_o	0.1	0.1	+40	84 ± 12	1.2 ± 0.5	0.051 ± 0.036	3	4 A
8	P_o	1.0	0.1	+40	1,600 ± 1,000	2.6 ± 7.9	0.16 ± 0.05	11	–
9	F_o	0.1	0.1	+40	73 ± 29	1.3 ± 1.0	3.4 ± 0.5	5	4 B
10	τ_o	0.1	0.1	+40	506 ± 83	1.0 ± 3.0	3.2 ± 2.0	5	4 C
11	P_o	0.1	3.0	−40	18,000 ± 5,000	1^{^a}	0.78 ± 0.12	6	–
12	P_o	0.1	3.0	+40	>10⁵	–	0.88 ± 0.05	6	–
13	F_o	0.1	3.0	−40	2,400 ± 2,000	0.7 ± 1.2	70 ± 15	9	6 A
14	τ_o	0.1	0.1	−40	123 ± 23	1.9 ± 1.6	10.0 ± 3.4	6	6 B
15	τ_o	0.1	3.0	−40	480 ± 100	2.2 ± 2.0	73.0 ± 4.0	9	6 B
16	τ_o	0.1	10	−40	790 ± 150	1.5 ± 1.3	16.0 ± 7.0	7	6 B

No.		[Ca²⁺]_L mM	[Ca²⁺]_C μM	V mV	K_i μM	n_i	P_max, F_max, and τ_max	n	Figure
1	P_o	0.1	0.1	−40	45 ± 5	1.8 ± 0.8	0.33 ± 0.07	17	3 A, 4 A
2	P_o	1.0	0.1	−40	800 ± 180	1.5 ± 1.3	0.071 ± 0.020	11	3 A, 4 A
3	F_o	0.1	0.1	−40	76 ± 27	1.3 ± 1.0	8.8 ± 1.1	6	3 B, 4 B, 6 A
4	F_o	1.0	0.1	−40	876 ± 224	1.3 ± 1.0	11.8 ± 0.9	9	3 B, 4 B
5	τ_o	0.1	0.1	−40	123 ± 23	1.9 ± 1.6	10.0 ± 3.4	6	3 C, 4 C, 6 B
6	τ_o	1.0	0.1	−40	1,000 ± 330	2^{^a}	9.4 ± 5.0	9	3 C, 4 C
7	P_o	0.1	0.1	+40	84 ± 12	1.2 ± 0.5	0.051 ± 0.036	3	4 A
8	P_o	1.0	0.1	+40	1,600 ± 1,000	2.6 ± 7.9	0.16 ± 0.05	11	–
9	F_o	0.1	0.1	+40	73 ± 29	1.3 ± 1.0	3.4 ± 0.5	5	4 B
10	τ_o	0.1	0.1	+40	506 ± 83	1.0 ± 3.0	3.2 ± 2.0	5	4 C
11	P_o	0.1	3.0	−40	18,000 ± 5,000	1^{^a}	0.78 ± 0.12	6	–
12	P_o	0.1	3.0	+40	>10⁵	–	0.88 ± 0.05	6	–
13	F_o	0.1	3.0	−40	2,400 ± 2,000	0.7 ± 1.2	70 ± 15	9	6 A
14	τ_o	0.1	0.1	−40	123 ± 23	1.9 ± 1.6	10.0 ± 3.4	6	6 B
15	τ_o	0.1	3.0	−40	480 ± 100	2.2 ± 2.0	73.0 ± 4.0	9	6 B
16	τ_o	0.1	10	−40	790 ± 150	1.5 ± 1.3	16.0 ± 7.0	7	6 B

The luminal Mg²⁺ dependencies of P_o were characterized by fitting data shown in the figures plus additional data not shown with Hill curves using the following equation for inactivation:

\[P_{o}{=}\frac{P_{\mathrm{max}}}{1{+}\left([Mg^{2{+}}]/K_{i}\right)^{n_{i}}}.\]

P_max is the maximal activity of the channel in the absence of luminal Mg²⁺, K_i is the [Mg²⁺] for half-inhibition, and n_i is the Hill coefficient. Similar equations were used to fit F_o and τ_o. The equations were fitted with the data using the method of least squares. n is the number of channels studied.

The Hill coefficient was fixed during fitting.

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