THYROXINE AFFECTS VENTILATION, LUNG MORPHOMETRY, AND NECROSIS OF DIAPHRAGM IN DYSTROPHIC HAMSTERS

Male dystrophic hamsters (DH) were treated with pellets containing thy roxine (T hamsters) or placebo (P hamsters) for 8 wk. O-2 consumption, ventilation, and ventilation in response to 8% CO2 in O-2 and 10% O-2 in N-2 were evaluated 1 and 8 wk after treatment began. O-2 consumpti on was elevated in T hamsters at 1 and 8 wk, whereas ventilation was s imilar in the two groups on the first week. By 8 wk, ventilation and v entilatory responses to hypoxic and hypercapnic challenges were 100% g reater in T than in P hamsters (P < 0.05). Morphemetric evaluations at the end of the treatment period indicated that air space surface dens ity, tissue volume density, and surface density-to-air space volume ra tio of the lung parenchyma were greater (P < 0.05) in T than in P hams ters. In contrast, chord length within the lung parenchyma was shorter and necrosis in the diaphragm and tongue, but not in the heart, was l ower (P < 0.05) in T than in P hamsters. Taken together, these results suggest that T treatment of DH for 8 wk affects O-2 consumption, vent ilation, lung architecture, and skeletal muscle without increasing tri iodothyronine levels.