[rat-forum] RE: [rat-forum] How much allelic polymorphism is seen in common outbred strain?

mfesting nobody at no-reply.mcw.edu
Tue Mar 25 08:46:00 CST 2003


In the far off days before DNA markers became available David Lovell and I did a morphometric study of the mandible shape of 88 samples of 6-38 male rats/sample from 41 separate colonies including six inbred strains 15 colonies of outbred "Wistar" rats (from 10 suppliers) 9 colonies of outbred "Sprague-Dawley" rats (from 7 suppliers) and 4 colonies of outbred Hooded rats.


All of the inbred strains were easily identifiable  by their mandible shape, "...however, the data given here show that Wistar and Spargue-Dawley outbred rats in the UK are heterogeneous with substantial overlap between the two types. Research workers should not assume that two colonies of Wistar rats are genetically identical, and they certainly should not asume that Sprague-Dawley and Wistar rats in the UK are the same as those in the USA. Anyone wishing to be able to use an internationally distributed named strain with some asurance that it is genetically identical with other colonies with the same name should use an inbred strain such as F344 or LEW" (Lovell and Festing 1982 The Journal of Heredity 73:81-82.).


A study of 21 biochemical markers in three Wistar and two Sprague-Dawley stocks of rats  (Katoh, H 2000 International Harmonization of laboratory animals, In:International Committee of the Institute of Laboratory Animal Research, editor, . Microbial status and genetic evaluation of mice and rats. Washington, DC: National Academy Press.  pp. 97-104.) shows differences between nominally identical stocks, however, although all the data are given in a table genetic distances have not been calculated. That would be an interesting thing to do. But, for example, the frequency of the  Es2a allele is 1.0, .91 and 0.0 in the three Wistar colonies and  0.76 and 0.31 in the two SD stocks.


Differences between "Wistar" stocks for characters of biomedical importance have also sometimes been recorded. For example Ryle PR et al (1996. Survival in rat carcinogenicity studies: a comparison of Wistar rat obtained from two sources. B&K Science Now 5:1-4.) studied survival and pathology of Wistar rats from two commercial sources and found substantial differences between them in body weight, food consumption, and survival to 2-years( 59% male, 53% female in one stock, 83% male 78% female in the other). I don't know if this has been written up the real scientific literature. Another paper that may be of interest is MacKenzie WF, Garner FM. 1973. Comparison of neoplasms in six sources of rats. Journal of the National Cancer Institute 50:1243-1257. It is some time since I have read it, and do not have a reprint, but I think that it records differences in nominally identical rats.


For those interested in a more general review of genetic variation in the response of rat strains to pharmacological agents a starting point might be Kacew S, Festing MFW. 1996. Role of rat strain in the differential sensitivity to pharmaceutical agents and naturally occurring substances. Journal of Toxicology and Environmental Health 47:1-30., and a short review of the failure of toxicologists to take account of genetics in research and testing is Festing MFW. 2000. Rat Genetics and Toxicology. In:International Committee of the Institute of Laboratory Animal Research, editor, . Microbial status and genetic evaluation of mice and rats. Washington, DC: National Academy Press.  pp. 97-104.


Best wishes to you all,


Michael Festing









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