Effects of long-term hypergravity on muscle, heart and lung structure of mice.
Quantitative changes in lung, heart and muscle structure were assessed in mice exposed for 14 weeks to a gravitational field of 3 G since the age of 4 weeks; matched controls were kept at normal gravity (1 G). The body mass of 3-G-exposed mice was significantly reduced by 9%, while total skeletal muscle mass remained the same fraction of body mass. The mass of the soleus muscle was found to be significantly larger in 3-G-exposed mice both in absolute (+27%) and body mass specific terms (+42%). Capillary density was significantly reduced by 22% because of a relatively larger increase of fiber cross-sectional area (+47%) than of capillary to fiber ratio (+16%). Other morphometric variables remained unchanged with hypergravity. Heart mass and mitochondrial volume were both larger in 3-G-exposed mice (+15% and +27%, respectively). This difference reached statistical significance when normalized to body mass. The only significant difference in lung structure detectable by morphometric methods were a smaller volume (-9%), that paralleled lower body mass, and thinner alveolar septa (-12%). From these results it is concluded that the lung's support structures in mice are sufficiently strong to withstand the stress of long-term hypergravity; however, 3-G exposure leads to a selective hypertrophy of soleus muscle fibers while absolute capillary length in this muscle remains unaltered.
Frey
M
M
University of Bern, Department of Anatomy, Switzerland.
von Känel-Christen
R
R
Stalder-Navarro
V
V
Duke
P J
PJ
Weibel
E R
ER
Hoppeler
H
H
D000222:Adaptation, Physiological; D000818:Animals; D001835:Body Weight / Q000502:physiology; D005260:Female; D006321:Heart / Q000502:physiology; D018471:Hypergravity; D008168:Lung / Q000502:physiology / Q000648:ultrastructure*; D051379:Mice; D008813:Mice, Inbred ICR; D018482:Muscle, Skeletal / Q000502:physiology / Q000648:ultrastructure*; D009206:Myocardium / Q000648:ultrastructure*; D009929:Organ Size / Q000502:physiology; D011650:Pulmonary Alveoli / Q000502:physiology / Q000648:ultrastructure*