HGF protein levels after muscle injury in WT, uPA^−/−, and PAI-1^−/− mice. Muscles from WT, uPA^−/−, and PAI-1^−/− mice collected from uninjured control mice (Con) and on days 1, 3, 5, and 10 after cardiotoxin injury. (Top) Muscle homogenates subjected to heparin sulfate affinity purification and then Western blotting for HGF. An equal amount (2.5 ng) of an HGF standard (Std) was loaded onto each gel. SC indicates single chain; and αC: α-chain. (Bottom) Densitometric measurements performed for total HGF (single chain + α-chain) and active α-chain HGF. Total HGF normalized to HGF standard on each blot, and α-chain normalized to total HGF in each sample. Bars represent mean ± SE; n = 4 to 6 per time point. *Mean value significantly smaller than that for WT mice (P < .05). **Mean value significantly larger than that for WT mice (P < .05).