FIGURE 7.

The effects of the cTnI-R21C mutation on SR Ca²⁺ release in the presence and absence of ISO. Shown is functional SR Ca²⁺ content as measured by the Ca²⁺ transient amplitude during 20 mmol/liter caffeine-induced contractures in cardiomyocytes isolated from old (15 months) WT and R21C mice. Black and gray vertical bars represent the presence and absence of 100 nmol/liter isoproterenol, respectively, in the myocyte perfusion bath. *, p < 0.05 versus WT +ISO; §, p < 0.01 versus WT −ISO. Error bars, S.E.