Sustained Overexpression of IGF-1 Prevents Age-Dependent Decrease in Charge Movement and Intracellular Ca2+ in Mouse Skeletal Muscle

AbstractIn this work we tested the hypothesis that transgenic sustained overexpression of IGF-1 prevents age-dependent decreases in charge movement and intracellular Ca2+ in skeletal muscle fibers. To this end, short flexor digitorum brevis (FDB) muscle fibers from 5–7- and 21–24-month-old FVB (wild-type) and S1S2 (IGF-1 transgenic) mice were studied. Fibers were voltage-clamped in the whole-cell configuration of the patch-clamp technique according to described procedures (Wang, Z. M., M. L. Messi, and O. Delbono. 1999. Biophys. J. 77:2709–2716). Charge movement and intracellular Ca2+ concentration were recorded simultaneously. The maximum charge movement (Qmax) recorded in young wild-type and transgenic mice was (mean±SEM, in nC μF−1): 52±2.1 (n=46) and 54±1.9 (n=38) (non-significant, ns), respectively, whereas in old wild-type and old transgenic mice the values were 36±2.1 (n=32) and 49±2.3 (n=35), respectively (p<0.01). The peak intracellular calcium [Ca2+]i recorded in young wild-type and transgenic mice was (in μM): 14.5±0.9 and 16±2.1 (ns), whereas in old wild-type and transgenic mice the values were 9.9±0.1 and 14±1.1 (p