The research you mentioned specifies in the abstract a probable cause for failing to replicate the same conditions for the experiment: It is possible that during a colony conversion the supplier inadvertently introduced strain differences making the present rats more resistant to xenobiotic consumption.

In my opinion this tells a lot.

BTW: There are other researchers that replicated similar results on similar experiments too: http://www.ncbi.nlm.nih.gov/pubmed/11072395?dopt=Abstract

So is better to see all the experiments to avoid bias.