rat unit


Also found in: Acronyms.

rat unit

An obsolete, semi-quantitative unit corresponding to the minimum amount of an oestrogenic substance required to produce characteristic desquamation of vaginal epithelium in ovarectomised rats.

rat unit

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R.U.

The greatest dilution of estrogen that will cause desquamation and cornification of the vaginal epithelium if given to a mature spayed rat in three injections, one every 4 hr.