Table 1. Effect of MgATP in the cytoplasmic (cis) solution on RyR activity.

Single-channel parameters under control conditions and in the presence of 2 mM MgATP and 10⁻⁵ M cis Ca²⁺ at +40 or −40 mV. Data are given (means±S.E.M.) for open probability (P_o), mean open time (T_o) and mean closed time (T_c). Asterisks (*) indicate a significant difference between the initial reference value and the parameter value with MgATP. Data for 10⁻⁴ M cis Ca²⁺ is from [13] and is included here for comparison.

		+40 mV		−40 mV
cis [Ca2+]		10−5 M (n=5)	10−4 M (n=10)	10−5 M (n=5)	10−4 M (n=10)
Po	Initial	0.293±0.149	0.25±0.08	0.256±0.141	0.17±0.08
	+MgATP	0.201±0.084	0.40±0.11*	0.169±0.016	0.38±0.09*
To(ms)	Initial	49.4±44.5	26.2±22.4	42.7±40.6	22.8±20.3
	+MgATP	76.8±36.1*	45.6±20.1*	49.7±28.2	26.9±15.3*
Tc (ms)	Initial	198.9±107.1	42±56.2	82.9±63.3	161±57
	+MgATP	132.4±56	76±30.5	124.2±92.1	67±47*