Fig. 5.

Proteolytic function of Calpain-3 is not required for SR calcium kinetics.

(A, B) Myofibers isolated from FDB muscle of WT and Capn3^CS/CS mice were loaded with Fura2FF/AM, twitch activated and Ca²⁺ transients were measured. The time required for the decay of Fura2FF/AM fluorescence from 90 to 10% of its peak was used to determine the speed of Ca²⁺ influx from the cytosol to the SR (A). Ca²⁺ efflux from the SR to the cytosol was measured by the ratio of Ca²⁺ bound to Ca²⁺ unbound fluorescence upon myofiber stimulation (B). There was no significant difference in Ca²⁺ influx and speed of efflux between WT and Capn3^CS/CS. The numbers of measured myofibers from WT and Capn3^CS/CS were 24 and 22, respectively. Error bars, SE.