Thyroxine affects ventilation, lung morphometry, and necrosis of diaphragm in dystrophic hamsters.

Male dystrophic hamsters (DH) were treated with pellets containing thyroxine (T hamsters) or placebo (P hamsters) for 8 wk. O2 consumption, ventilation, and ventilation in response to 8% CO2 in O2 and 10% O2 in N2 were evaluated 1 and 8 wk after treatment began. O2 consumption was elevated in T hamsters at 1 and 8 wk, whereas ventilation was similar in the two groups on the first week. By 8 wk, ventilation and ventilatory responses to hypoxic and hypercapnic challenges were 100% greater in T than in P hamsters (P < 0.05). Morphometric evaluations at the end of the treatment period indicated that air space surface density, tissue volume density, and surface density-to-air space volume ratio of the lung parenchyma were greater (P < 0.05) in T than in P hamsters. In contrast, chord length within the lung parenchyma was shorter and necrosis in the diaphragm and tongue, but not in the heart, was lower (P < 0.05) in T than in P hamsters. Taken together, these results suggest that T treatment of DH for 8 wk affects O2 consumption, ventilation, lung architecture, and skeletal muscle without increasing triiodothyronine levels.