Figure 4

Ca²⁺ movement in primary skeletal myotubes. Caffeine (a), which is a direct RyR1 agonist or KCl (b), a membrane depolarizer, was applied to myotubes treated with sildenafil, and Ca²⁺ movement from the SR to cytosol in myotubes was measured. Histograms are shown for the normalized peak amplitude to the mean value of those from an untreated control. The results are presented as the means±s.e. for the number of experiments in the parentheses in Table 2. *, and the significant difference was compared with untreated controls (P<0.05). Ca²⁺ release in primary skeletal myotubes in response to both caffeine and KCl as significantly enhanced by sildenafil.