Dose-dependent effects of hypergravity on body mass in mature rats.
BACKGROUND
Previous reports have shown that exposure to hypergravity decreases rat body mass during the initial phase, with this decrease and level of gravity showing a dose-response relationship. The present study examined whether rate of body mass gain after the initial phase of exposure is attenuated by hypergravity in a dose-dependent manner and sought to identify any threshold.


METHODS
Male 10-wk-old rats (n = 64) were used, with 16 rats serving as 1.0-G controls, and 48 rats exposed to hypergravity for 14 d in 4 groups (1.5, 2.0, 2.5, and 3.5 G; n = 12 each). Body mass gain was evaluated according to slope of change in body mass from day 7 of exposure to hypergravity, as both absolute and relative values.


RESULTS
Slopes of body mass gain did not differ between the 1.0- and 1.5-G groups (6.09 and 5.75 g x d(-1), respectively), but were significantly less for the 2.0-, 2.5-, and 3.5-G groups (4.91, 3.03 and 1.99 g x d(-1), respectively) than for the 1.0- and 1.5-G groups. Body mass gain as a relative value did not differ between the 1.0-, 1.5-, and 2.0-G groups (1.5 +/- 0.2, 1.6 +/- 0.6 and 1.4 +/- 0.3 g x d(-1) x 100 g(-1) body mass, respectively), but was significantly less for the 2.5- and 3.5-G groups (1.1 +/- 0.6 and 0.8 +/- 0.3 g x d(-1) x 100 g(-1) body mass, respectively) than for the 1.0-, 1.5-, and 2.0-G groups. Absolute values and rate of body mass gain were reduced with increases in gravity.


CONCLUSIONS
Exposure to hypergravity attenuates body mass gain in a dose-dependent manner, with a threshold possibly existing between 1.5- and 2.5-G for 10-wk-old male rats.
Kita
Sayaka
S
Department of Hygiene and Space Medicine, Nihon University School of Medicine, Tokyo, Japan.
Shibata
Shigeki
S
Kim
Hyeteok
H
Otsubo
Akira
A
Ito
Masao
M
Iwasaki
Ken-ichi
K
D000818:Animals; D015992:Body Mass Index; D001835:Body Weight; D002498:Centrifugation; D004734:Energy Metabolism; D018471:Hypergravity; D008297:Male; D023421:Models, Animal; D051381:Rats; D017208:Rats, Wistar