Organ Growth Functions in Maturing Male Sprague-Dawley Rats Based on a Collective Database

Abstract

Ten different organ weights (liver, spleen, kidneys, heart, lungs, brain, adrenals, testes, epididymes, and seminal vesicles) of male Sprague-Dawley (S-D) rats of different ages (1–280 d) were extracted based on a thorough literature survey database. A generalized Michaelis–Menten (GMM) model, used to fit organ weights versus age in a previous study (Schoeffner et al., 1999) based on a limited data, was used to find the best fit model for the present expanded data compilation. The GMM model has the functional form: Wt = (Wt_o.K ^γ + Wt_max.Age ^γ)/(K ^γ + Age^γ) where Wt is organ/tissue weight at a specified age, Wt_o and Wt_max are weight at birth and maximal growth, respectively, and K and γ are constants. Organ weights were significantly correlated with their respective ages for all organs and tissues. GMM-derived organ growth and percent body weight (%BW) fractions of different tissues were plotted against animal age and compared with experimental values as well as previously published models. The GMM-based organ growth and %BW fraction profiles were in general agreement with our empirical data as well as with previous studies. The present model was compared with the GMM model developed previously for six organs—liver, spleen, kidneys, heart, lungs, and brain—based on a limited data, and no significant difference was noticed between the two sets of predictions. It was concluded that the GMM models presented herein for different male S-D rats organs (liver, spleen, kidneys, heart, lungs, brain, adrenals, testes, epididymes, and seminal vesicles) are capable of predicting organ weights and %BW ratios accurately at different ages.

Special thanks go to Dr. Lynne Haber for providing us with the helpful rat organ weight database introduced in Gentry et al. (2004). This project was supported by U.S. EPA STAR grant R830800.