Unlike all known strains of rat, the androgeninducible α2u-globulin gene family is totally silent in the liver of NIH black (NB) rats. No endocrinological or reproductive abnormalities are apparent, and the mRNA for the androgenrepressible hepatic protein SMP-2 is normally regulated in these animals. Furthermore, immunoblot analysis shows a normal level of the male-specific cytoplasmic androgen-binding protein. Cross-breeding of the NB male and Sprague-Dawley female shows that the hybrid male in the F-l generation regains the androgen-dependent expression of α2u-globulin in the liver. These results along with the observation of high constitutive level ofα2u-globulin mRNA in the preputial gland of NB rats indicate a tissue- and gene-specific regulatory defect which prevents androgenic induction of α2u-globulin in the liver.
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