D-limonene is a naturally occurring substance found mainly in citrus oils and is used as a flavor and fragrance additive in food, cleaning products, even shampoo. It's also found in black pepper, nutmeg, and mango. In oranges, as far as I can tell, d-limonene is mostly or entirely in the orange rind and gets into the juice either during the juicing process or as an additive. People I know who have fed their rats oranges have had no problems. I can only speculate that maybe this is because they don't eat the rinds, or maybe because some domestic male rats don't have this problem. I don't know, but I'm not taking any chances on the second guess! If it happens with so many strains of lab rats, it probably happens in our rats.
Of course you wouldn't want your rat to get anything near the TD50 dose, much smaller amounts will increase the cancer risk. On the other hand, to reach the TD50 dose of orange juice you would have to give your rat nothing but orange juice (instead of water) every day for at least a couple months. Thus, I wouldn't worry too much if you've given your rat a taste of orange juice before. I just wouldn't do it again.
For anyone who wants to ask how you can get your rat enough vitamin C: rats make their own, so they don't need nearly as much as you. Humans are rare in the mammal world in not making their own vitamin C.
Copy machine toner, unleaded auto fuels, and some bathroom deodorizers also contain such male rat kidney cancer inducing chemicals. (In fact, the cancer warning you see at the gas pump is because of this!) But I don't think you are very likely to feed those to your rats.
I first heard about this from the NPR story "Rats and Mice Not Good for Testing Toxicity" by Richard Harris, Copyright 1992 National Public Radio. Additional information came from James Swenberg.
Common foods with d-limonene and TD50 values are from The Carcinogenic Potency Database (http://potency.berkeley.edu/herp.html). Note that they list some of the other chemicals that male rats are uniquely sensitive to.
Additional information came from National Toxicology Program (http://ntp-server.niehs.nih.gov/), the Florida Chemical Company, Inc. (http://www.floridachemical.com/) and probably half a dozen other toxicology reports I found when I searched for d-limonene on Google.