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Age-related changes in body composition in laboratory rats: Strain and gender comparisons
Citation:
Macphail, R., P. Phillips, C. Gordon, AND K. Jarema. Age-related changes in body composition in laboratory rats: Strain and gender comparisons. Presented at Society of Toxicology meeting, March 10 - 14, 2013.
Impact/Purpose:
This abstract will be presented at the Society of Toxicology meeting, March 10-14, 2013, San Antonio, TX
Description:
Long Evans (LE), Sprague Dawley (SD), Fischer 344 (F344), and Brown Norway (BN) rats are all commonly used as laboratory research subjects. These strains have been studied under many conditions, but few studies have measured changes in body composition as the animals age. Understanding strain differences with regard to body composition, age and growth are essential for understanding toxicity mechanisms, specifying deprivation regimens for studies on food- rewarded learning and performance, and developing accurate pharmacokinetic models of toxicity. This study used a Bruker body composition analyzer to compare the changes in body fat, lean tissue, and fluid for male (n1 2/strain) and female (nz 12/strain) LE, SD, F344 and BN rats. We found dramatic differences in body composition between the four rat strains. In both male and female rats, body weights were similar for the LE and SD strains, and much lower for the F344 and BN strains. In all cases, body weights for females were less than males. Lean mass for both genders followed a similar pattern as body weight, with the LE and SD rats differing from the BN and F344 rats, and males differing from females. Total fat content differed substantially between strains. The LE rats had the highest fat content, followed by SD, then F344, and finally BN, which had the lowest fat content. These strain differences were seen with both males and females. When body fat was calculated as a percentage of total body weight, the LE rats still had the highest values and the BN rats had the lowest values. However, the male SD and F344 rats appeared to be nearly identical in percent fat. Moreover, the female SD and F344 had similar percent fat values early in development, but these values diverged as they continued to age. These results show marked differences in body composition between four rat strains commonly used in toxicology research. (This is an abstract of a proposed presentation and does not reflect US EPA policy.)