Figure 6

Hyperglycemia induces selective depletion of diaphragm troponin T. Representative western blots and mean densitometry of key contractile proteins from diaphragm homogenates from control (black), hyperglycemic (red), hyperglycemic + PEG-SOD (blue), and hyperglycemic + denatured (heat inactivated) PEG-SOD groups (n = 6 for each comparison). Images were obtained from the same gel, but lanes were not adjacent and are demarcated by the lines within the representative image. Actin levels are shown in A), actinin levels in B), tropomyosin levels in C) and troponin T levels in D). Blots were reprobed with tubulin as a loading control. Densitometry is presented in arbitrary units and was normalized to control values. There were no significant differences in the protein contents of actin, actinin, or tropomyosin between groups. On the other hand, troponin T levels were significantly decreased with hyperglycemia; this loss of troponin T was prevented with administration of PEG-SOD, but not with denatured PEG-SOD (P <0.001). These data demonstrate that a superoxide scavenger preserves hyperglycemia -induced loss of troponin T in the diaphragm. (* significantly different from control and hyperglycemic + PEG-SOD groups). PEG-SOD, polyethylene glycol superoxide dismutase.