BROWN NORWAY Rat

This strain was created by BILLINGHAM and SILVERS in 1958, from a brown mutation maintained by D.H. KING and P. APTEKMAN in a pen-bred colony (BILLINGHAM and SILVERS, 1959), probably from wild-caught rats (RUSSEL-LINDSAY, 1979).

90 % have a life expectancy greater than 25 months, 50 % of them reach 32 to 35 months.

BROWN NORWAY rats have high rates of spontaneous bladder carcinoma (28-35 % in males, 2-3 % in females) and ureter carcinoma (6-9 % in males and 20-22 % in females). Other common tumours in males are pancreas islet adenoma (15 %), pituitary adenoma (14 %), lymphoreticular sarcoma (14 %) and in the females, pituitary adenoma (26 %), adrenal cortical adenoma (19 %), vaginal sarcoma (19 %), mammary gland fibro-adenoma (11 %). Also described is the females’ risk of cancer and metastasis increasing with age.
Another characteristic of the BROWN NORWAY strain is its important rate of endocardial disease in older animals.

Important notice: JANVIER LABS BROWN NORWAY rats have a retinal dystrophy caused by progressive loss of photoreceptors. Histology reveals that rods and cones disappear and a dysplasia of the outer nuclear layer with sectorial hyperplasia/hypernuclearity up to the retinal pigment epithelium. This peculiar aspect of the retina is similar to the one seen in some types of canine retinal dysplasia, in which the retina forms folds with round clumps (these are nevertheless absent in rats).

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