The Advantages of Sprague Dawley Rats in Research of Radiation-induced Thrombocytopenia

Laboratory rats have been used in medical research since the early twentieth century; their use for such purposes has grown in popularity to the point that they are utilized 50% more frequently than laboratory mice. Domesticated lab rats offer advantages over wild rats due to their more docile temperaments and documented genetic backgrounds. Particularly, lab rats have been instrumental in cancer research (Suckow, Weisbroth & Franklin, 2005). This prior success makes the lab rat an ideal choice for our proposed project, analyzing the influence of sweet potato extract on platelet recovery rates caused by Radiation-induced Thrombocytopenia.

The increased popularity of lab rats used for research purposes over time induced a concurrent increase in lab rat stock and strain diversity. Inbred rat strains offer genotypic reliability and as such are useful in genetic research. Particular inbred strains also display reliable phenotypic tendencies that are useful for research, such as the bio-breeding rat that spontaneously develops type I diabetes. However, since our project focuses not on genetics but the dosage-response relationship of potential radiation treatment on platelet counts, inbred strains are not necessary. Therefore, outbred lab rat stocks were available to us as well, and we chose to pursue this route.  

The oldest and perhaps most popular outbred lab rat used in biological and medical research is the albino Wistar rat. It was originally developed in 1906 by Henry Donaldson, Milton J. Greenman, and Helen Dean King; Wistar rats also served as the genetic predecessors of other popular lab rats such as the Long–Evans rat, and the rat we are choosing for our project, the Sprague Dawley rat. 

Both the Wistar rat and the Sprague Dawley rat are popular choices for use in medical research (Drachman, Root, & Wood, 1966; Horuichi et al., 1976; Laupacis et al., 1983). Their previous successful utilization in non-genetic dose-response testing makes them both ideal candidates for this project. However, due to behavioral and morphologic reasons, we have decided to use Sprague Dawley rats. Each rat stock type has distinctive phenotypic characteristics. While the Wistar is an appropriate and popular all-around model candidate, the Sprague Dawley rat is also popular due to their relatively calmer demeanor, larger sizes, and growth rates- Sprague Dawley rats gain 400 g by 12 weeks on average while Wistar rats gain approx. 350 g (Carere & Maestripieri, 2013). The nature of our project means that we will be constantly be handling the rats for sweet potato extract treatments and blood extractions; calmer rats will make this process much easier. In addition, the larger size of Sprague-Dawley rats makes them better candidates for projects such as ours that require drawing blood multiple times over prolonged periods. 

In addition, there is an abundance of research in which the blood of Sprague Dawley rats is analyzed after exposure to plant extracts. Nevin and Rajamohan (2008) measured blood coagulation factors in Sprague Dawley rats after exposure to virgin coconut oil treatments, while Peluso, Winters, Shanahan, and Banz (2000) analyzed Sprague Dawley platelet sensitivity under different levels of soy extract. The effect of blood platelet concentration collected from female Sprague Dawley rats on the recovery rate of Achilles tendon injuries has been analyzed as well (Aspenberg & Virchenko, 2004). We believe that this successful history of use in the research, in addition to their conducive behavioral and morphologic factors, make the Sprague Dawley rat an ideal candidate for our project analyzing the influence of sweet potato extract on platelet recovery rates caused by Radiation-induced Thrombocytopenia.

References

Aspenberg, P., & Virchenko, O. (2004). Platelet concentrate injection improves Achilles tendon repair in rats. Acta Orthopaedica Scandinavica, 75(1), 93-99.

Carere, C., & Maestripieri, D. (Eds.). (2013). Animal personalities: behavior, physiology, and evolution. University of Chicago Press.

Drachman, R. H., Root, R. K., & Wood, W. B. (1966). Studies on the effect of experimental nonketotic diabetes mellitus on antibacterial defense: I. Demonstration of a defect in phagocytosis. Journal of Experimental Medicine, 124(2), 227-240.

Horiuchi, N., Suda, T., Sasaki, S., Takahashi, H., Shimazawa, E., & Ogata, E. (1976). Absence of regulatory effects of 1α, 25-dihydroxyvitamin D3 on 25-hydroxyvitamin D3 metabolism in rats constantly infused with parathyroid hormone. Biochemical and Biophysical Research Communications, 73(4), 869-875.

Laupacis, A., Gardell, C., Dupre, J., Stiller, C. R., Keown, P., Wallace, A. C., & Thibert, P. (1983). Cyclosporin prevents diabetes in BB Wistar rats. The Lancet, 321(8314-8315), 10-12.

Nevin, K. G., & Rajamohan, T. (2008). Influence of virgin coconut oil on blood coagulation factors, lipid levels and LDL oxidation in cholesterol-fed Sprague–Dawley rats. e-SPEN, the European e-Journal of Clinical Nutrition and Metabolism, 3(1), e1-e8.

Peluso, M. R., Winters, T. A., Shanahan, M. F., & Banz, W. J. (2000). A cooperative interaction between soy protein and its isoflavone-enriched fraction lowers hepatic lipids in male obese Zucker rats and reduces blood platelet sensitivity in male Sprague-Dawley rats. The Journal of Nutrition, 130(9), 2333-2342.

Suckow, M. A., Weisbroth, S. H., & Franklin, C. L. (Eds.). (2005). The laboratory rat. Elsevier.