ABSTRACT
The laboratory rat is one of the most extensively used animal models in biomedical research. The modern laboratory rat is considered to be derived from naturally occurring albino mutants of the wild Norway rat (Rattus norvegicus), which originated in China but is now found on all continents except Antarctica. Albino Norway rats were bred in the nineteenth century as show animals and eventually became utilized in research laboratories. Phenotypic differences between rats of different genetic backgrounds can be quite useful when modeling particular diseases. However, these differences also have a considerable impact on many research endpoints. In rats, urine may be collected by free catch, timed collection into metabolic cages, and cystocentesis, catheterization, or cystotomy at necropsy. Clinical chemistry parameters that are consistently higher in males compared to female rats are serum ALP and triglycerides, and urine protein and ketones.
