Figure 5

Hyperglycemia reduces single fiber contractile force generation in all fiber types. Fiber typing was performed for each diaphragm fiber in which force-pCa relationships were determined and then evaluated to assess if the changes in force were related to a specific fiber type. A total of 346 fibers were typed and subsequently classified as Type I (slow), Type IIA, Type II B, Type IIX, Type IIB/X and mixed based on the migration pattern of myosin heavy chains (determinations were not made for 14 fibers due to technical issues). A) depicts a representative gel for determination of individual fiber type. The first lane is a protein standard obtained from total diaphragm homogenates which contains all myosin heavy chain isoforms, the other lanes indicate myosin heavy chain isoforms from individual fibers. The image was obtained from the same gel, but lanes were not adjacent and are demarcated by the lines within the representative image. B) represents the effect of fiber type on maximal single fiber contractile force generation in response to hyperglycemia, hyperglycemia + PEG-SOD and hyperglycemia + denatured (heat inactivated) PEG-SOD. The absolute force generation/CSA in kPa is indicated for the different fiber types from the four experimental groups. As shown, hyperglycemia reduced single fiber contractile force generation in all diaphragm fiber types. Administration of PEG-SOD, but not denatured PEG-SOD, largely restored contractile force generation in single permeabilized diaphragm fibers independent of fiber type (P < 0.001, * significantly different when compared to control and hyperglycemia + PEG-SOD fibers). PEG-SOD, polyethylene glycol superoxide dismutase.