Expression of specific IGFBPs is associated with those of the proliferating and differentiating markers in regenerating rat plantaris muscle.

To examine the relationship between specific insulin-like growth factor (IGF)-binding proteins (IGFBPs) and myogenesis during muscle regeneration in vivo, we measured mRNA expression of IGFBPs and myogenic markers in rat plantaris muscle after bupivacaine administration. IGF-I Ea, MGF, IGFBPs and myogenic marker mRNAs were analyzed 12, 24, 48 and 72 h after bupivacaine injection. IGFBP-1, -2, -3 and -4 proteins were immunostained after the treatment. MGF, IGF-I Ea and IGFBP-4 mRNAs started to increase 12 or 24 h after bupivacaine injection and increased further after that. IGFBP-1, -2, -3 and -4 proteins were strongly stained in the immature muscle fiber nuclei and the extracellular matrix after bupivacaine injection. PCNA, MyoD, IGFBP-2 and IGFBP-3 mRNAs increased at 12 or 24 h and did not show further increases after that. Myogenin, p21, IGFBP-1 and IGFBP-5 mRNAs sharply increased after 72 h. These results suggest that specific IGFBPs are individually expressed and differently associated with the expression of myogenic markers in regenerating muscles.