Figure 2.

Pooled data of diastolic (open symbols) and systolic (closed symbols) [Ca²⁺]_i (a) and twitch force (b) in wild-type (n = 6) and mutant muscles (n = 6–7) at varied [Ca²⁺]_o. Both systolic [Ca²⁺]_i and force increased at higher [Ca²⁺]_o, with no changes in diastolic [Ca²⁺]_i and force in both groups. However, the systolic [Ca²⁺]_i is significantly higher in mutant muscles at [Ca²⁺]_o > 3.0 mM (P < 0.03), with no changes in twitch force between the two groups. All muscles were stimulated at 0.5 Hz at room temperature. Data are means ± SEM of at least six muscles from six individual animals.