Abstract
Estrogens injected into lactating rats have been shown to be transmitted to the suckling young inducing changes in urogenital organs of both sexes 1 The effects are of such a nature that it seemed advisable to make further observations on similar animals, at intervals after cessation of treatment, in order to determine the permanency of the condition and the course of any subsequent changes. It has been reported that female rats given prepuberal injections of androgen2-4,6 or estrogen5-7 have severe reproductive deficiencies as adults. Because of variations in Methods of administration, hormones used, and length of treatment, the present study brings out differences thought to be of significance.
Methods. We have observed that in untreated female littermates of immature animals given daily injections of diethylstilbestrol, the vaginas open at the same time as in injected animals. This has been confirmed repeatedly with large litters containing only one injected animal. Similar changes have been observed in litters confined to cages in which stilbestrol was sprayed upon shavings used as nesting material. Injection of cagemates or contamination of nesting material with stilbeestrol may therefore be used as alternative methods of administering hormone to immature animals.
Five groups of rats, totalling 154 animals, were treated with estrogen for various lengths of time, the initial treatment being given at various times between birth and the 28th day of life. Animals of Group I were suckled by mothers injected with .1 mg stilbestrol daily; in those of Group II the mothers received .5 mg estrone daily. Group III received direct injections of .01 mg stilbestrol, while those of Group IV were affected by stilbestrol injected into littermates given .01 mg daily. Group V consisted of animals exposed to small quantities of environmental stilbestrol on nesting material.
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