Figure 1.

Changes of Ca²⁺ transients (a and c) and twitch force (b and d) in a representative mouse ventricular trabecula at 2.0, 4.0, and 8.0 mM [Ca²⁺]_o. The muscle was superfused with modified KH buffer and stimulated at 0.5 Hz. Increases in [Ca²⁺]_o from 2.0 to 8.0 mM increased systolic [Ca²⁺]_i from 0.61 to 1.51 mM, and twitch force from 9.8 to 42 mN/mm². There were no significant changes in diastolic [Ca²⁺]_i or force. [Ca²⁺]_i, intracellular Ca²⁺ concentration; [Ca²⁺]_o, extracellular Ca²⁺ concentration; KH, Krebs-Henseleit.