title: Dose-dependent effects of hypergravity on body mass in mature rats.
abstract: 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.
authors.affiliation: Department of Hygiene and Space Medicine, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Kita
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shibata
authors.forename: Hyeteok
authors.initials: H
authors.lastname: Kim
authors.forename: Akira
authors.initials: A
authors.lastname: Otsubo
authors.forename: Masao
authors.initials: M
authors.lastname: Ito
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Iwasaki
mesh_terms: 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