Table 1.

Composition of solutions used for relaxing and activating skinned fibers.

Solution	[K+]	[EGTA]	[HDTA]	[Mg2+]total	[Ca]total	[Ca2+]free	[Sr]total	[Sr2+]free
A	117	50	–	10.3	–	<10−6	–	–
B	117	50	–	8.12	49.5	0.02	–	–
H	117	0.2	49.8	8.51	–	<1.7 × 10−5	–	–
S	114	50	–	5.95	–	–	40	0.283

All solutions contained [mmol]: Na⁺ [36]; HEPES [60]; total ATP [8]; creatine phosphate (CP) [10]; and sodium azide [1]. pH was 7.10 ± 0.01 at 23–25°C. A = Relaxing solution. B = Ca²⁺ containing activating solution. H = Pre-activating solution. S = Sr²⁺ containing activating solution. Solutions were titrated using a pH metric method (Ashley and Moisescu, 1977).