Abstract
Summary. The female homozygote (jj) Gunn rats reach maturity before their heterozygote (Jj) sisters. This early onset of puberty is in 60% of the cases accompanied by ovulations. The heterozygote (Jj) rats reach maturity before normal (JJ) female rats. It is generally recognized that maturity is reached at a later age in poor environmental conditions, and under the influence of reduced water supply both the jj and the JJ rats matured later. The first opening of the vaginal orifice was equally postponed in JJ and jj rats, so that the difference between them was not altered. The fertility of the homozygote (jj) Gunn rats is not distinctly lower than that of the heterozygote (Jj) female animals. Accumulation of bilirubin in certain brain nuclei is not the cause of this precocious puberty. According to the literature the homozygote (jj) Gunn rats cannot glucuronize o-aminophenol, 4-methyl umbelliferone, o-aminobenzoate and bilirubin in the liver, kidneys, mucosa of stomach and duodenum or subcortical brain tissue. The heterozygote (Jj) rats can do so, but to a lesser extent than the normal ( JJ) rats. If one does not accept separate factors for the deficiency of glucuronyltransferase and for precocious puberty, there is room for the supposition that a deficiency of a certain glucuronyltransferase in the subcortical brain tissue affects the hypothalamic inhibiting centre and results in an early increase in hypophyseal gonadotrophic activity, and, consequently, in ovulatory precocious puberty.
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