BACKGROUND: Our previous study of rats exposed for 14 d to microgravity on Cosmos 2044 revealed morphological changes consistent with cardiac atrophy. METHODS: In the current comparison study, light and electron microscopic studies were performed on cardiac muscle from 10 rats exposed to hypergravity (continuous centrifugation at 2G) for 14 d. RESULTS: Myofiber area was significantly greater in the 2G papillary muscle as compared with muscle from 10 control rats of the same strain and size. This contrasts with the significant decrease in myofiber area previously seen in the rats exposed to microgravity. At the electron microscopic level, general morphological features were similar in both groups and resembled tissue from control rats from the previous Cosmos studies. However, mitochondria from papillary and ventricular muscle from the 2G rats revealed signs of fatigue typical of the early stage of hypertrophy. These results are consistent with a state of adaptive cardiac hypertrophy for the 2G group.
BACKGROUND: Our previous study of rats exposed for 14 d to microgravity on Cosmos 2044 revealed morphological changes consistent with cardiac atrophy. METHODS: In the current comparison study, light and electron microscopic studies were performed on cardiac muscle from 10 rats exposed to hypergravity (continuous centrifugation at 2G) for 14 d. RESULTS: Myofiber area was significantly greater in the 2G papillary muscle as compared with muscle from 10 control rats of the same strain and size. This contrasts with the significant decrease in myofiber area previously seen in the rats exposed to microgravity. At the electron microscopic level, general morphological features were similar in both groups and resembled tissue from control rats from the previous Cosmos studies. However, mitochondria from papillary and ventricular muscle from the 2G rats revealed signs of fatigue typical of the early stage of hypertrophy. These results are consistent with a state of adaptive cardiac hypertrophy for the 2G group.