AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 3 779-R785, Copyright © 1995 by American Physiological Society
Thyroxine affects ventilation, lung morphometry, and necrosis of diaphragm in dystrophic hamsters
E. H. Schlenker and J. A. Burbach
Department of Physiology, University of South Dakota School of Medicine, Vermillion 57069.
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.
