Fig. 1. Representative examples of protein oxidation (total carbonyl groups) immunoblots in the diaphragms (A ) of control (n = 8), moderate tidal volume (VT, n = 8), and high VT(n = 8) mechanically ventilated rats. Several oxidized proteins of different molecular weights (MW, in kilo Daltons) were observed in all muscles. Representative immunoblots of oxidized proteins of different MW, in kilodaltons, in the gastrocnemius (B ) of control, moderate-VT, and high-VTmechanically ventilated rats. Optical densities in the box plots are expressed as the ratio of the optical densities of total reactive carbonyl groups to those of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in each muscle. Standard box plots with median (twenty-fifth and seventy-fifth percentiles) and whiskers (at minimum and maximum values) are depicted. Reactive carbonyl levels were significantly reduced in the diaphragms (C ) of the high-VTrats compared with either control or moderate-VTanimals. In the gastrocnemius (D ), reactive carbonyls were significantly decreased in high-VTrats compared with controls and almost significantly reduced compared with moderate-VTrodents. In the soleus (E ) and tibialis anterior (F ), reactive carbonyl levels were significantly decreased in high- and moderate-VTrats compared with controls.