FIG 2.

NCX1 overexpression increases Na⁺-Ca²⁺ exchange. (A) Representative Fura-2 Ca²⁺ traces of forward-mode activity in WT and NCX1 TG (gray and red traces) and mdx and mdx NCX1 (green and blue traces) FDB muscle fibers at 2 to 4 months of age. The arrows indicate buffer changes. (B) SR Ca²⁺ store calculated from peak heights of 4-CMC Ca²⁺ transient in WT, NCX1 TG, mdx, and mdx NCX1 TG mice. (C) Time for 1/2 of the Fura-2 signal decay of the 4-CMC-induced Ca²⁺ transient during the forward-mode Na⁺-Ca²⁺ exchange experiment. *, P < 0.0001 versus WT. (D) Peak height of an electrically stimulated (paced) Ca²⁺ transient in Ringer's solution with 5 μM BTS using the Ca²⁺-sensitive dye Fura-2. *, P < 0.001 versus WT. (E) Time constant (Tau) fit to electrically stimulated transients for WT, NCX1 TG, mdx, and mdx NCX1 TG. (F) Amplitude of the repolarization of the membrane (afterhyperpolarization) of the action potential recorded in WT, NCX1 TG, mdx, and mdx NCX1 TG EDL muscle. *, P < 0.05 versus WT. The error bars indicate SEM. Numbers in the bars represent the number of fibers analyzed.