Figure 1. Phosphorylase activation is blunted in CK^−/− muscle during contraction.

EDL muscles from CK^−/− (^) and WT (•) mice were either not simulated (0 s) or stimulated with 330 ms tetani (1 s⁻¹) for 10 or 20 s in the absence or presence of 3 mm NaCN. Since NaCN did not significantly affect the results, they have been pooled. The 10 s stimulations were performed only in the absence of NaCN. Phosphorylase was measured in the absence and presence of 3.3 mm AMP and the fractional activity is the ratio of the two. Values are means ± s.e.m. for 8–18 muscles, except for WT at 10 s, where n = 2. CK^−/− values during contraction are significantly lower than for WT (P < 0.05).