Organ Weights and Fat Volume in Rats as a Function of Strain and Age

Abstract

The Fischer 344 (F344) rat and the Sprague-Dawley (SD) rat are used commonly to evaluate potential adverse health effects resulting from environmental exposure to chemicals. They are also the most common rat strain/stock used in physiologically based pharmacokinetic (PBPK) modeling. Accurate characterization of model input parameters will improve the usefulness of PBPK model predictions. Thus, organ (i.e., liver, kidneys, spleen, stomach, small intestine, large intestine, heart, lungs, brain) weights and body fat were measured in male SD rats of different ages (4 to 40 wk) and in young (9 to 10 wk) and old (22 to 23 mo) male F344 rats. Comparison of age-matched (9 to 10 wk) F344 and SD rats revealed that the SD rats weighed significantly more and had significantly higher absolute organ weights. These significant differences usually disappeared when organ weights were expressed as a percentage of body weight (relative organ weight). Percent body fat was significantly lower in the age-matched SD rats (6.48%) than in their F344 counterparts (8.67%). As expected, both body weight and absolute organ weights were significantly higher in old than in young F344 rats. However, these differences were largely reversed when relative organ weights were considered, with most relative organ weights significantly lower in the old F344 rats. Body fat as a percentage of body weight was 14.02% in the old F344 rats. When SD rats of various ages were examined, relative organ weights declined between the ages of 4 and 14 wk. In contrast, significant differences in percent body fat were not detected among the SD rats of different ages and weights examined in this study (4 to 40 wk, approximately 75 to approximately 450 g). In summary, values for physiological input parameters are provided that should prove useful in development and implementation of more accurate PBPK models.

Theory of nonexponential NMR signal decay in liver with iron overload or superparamagnetic iron oxide particles

“…In Eq. [19], a subscript f has been added to the symbol for chi to distinguish it from the magnetic susceptibility.…”

“…The dose was 18 mol Fe per kg body weight and the animals were sacrificed 1 hr after injection. In (9 -10-week-old SpragueDawley) rats, the liver constitutes about 3.9 Ϯ 0.2 percent of the body weight (19). Since 1 hr after injection about 82.6 Ϯ 0.3% of the ferumoxides is sequestered in the liver (10), we estimate a liver iron concentration of 0.021 Ϯ 0.001 mg Fe/g.…”

Evaluation of physiologically based pharmacokinetic models for use in risk assessment

“…Several efforts are underway at U.S. EPA to compile physiological parameters necessary for PBPK modeling into an electronic database format suitable for statistical analyses. The physiological parameters for specific subgroups is an area of active research and there are some published references for some parameter values (Luecke et al, 1994;Schoeffner et al, 1999;Haddad et al, 2001;Hattis et al, 2003;Price et al, 2003aPrice et al, , 2003bPelekis et al, 2003;Gentry et al, 2004).…”

Avaliação dos efeitos do LPS sobre parâmetros comportamentais e imunológicos em camundongos idosos

“…Em ambas linhagens, havia um progressivo aumento do peso corpóreo com a idade, e a partir de aproximadamente 14 a 16 meses 99 os animais começavam a apresentar perda de peso (Wirth-Dzieciolowska, Czuminska, 2000). Da mesma forma, ratos Fischer 344 idosos apresentaram maior peso corpóreo do que adultos, sendo que o peso relativo da gordura corpórea era maior nos ratos idosos (SCHOEFFNER et al, 1999).…”

“…Schoeffer et al (1999), além de observarem os pesos corpóreos de ratos em diferentes idades, também avaliaram a influência da idade no peso relativo de vários órgãos. Dos órgãos avaliados (fígado, baço, estômago, intestino delgado, intestino grosso, rins, coração, pulmões e cérebro) apenas o baço apresentava aumento do peso relativo com o avançar da idade (SCHOEFFNER et al, 1999). De forma semelhante, em um estudo sobre a exposição crônica a um poluente ambiental, camundongos fêmeas C57Bl/6 do grupo controle apresentaram aumento significativo do peso do baço com o avançar da idade, embora não tenha sido analisado o peso relativo (OUGHTON et al, 1995).…”