The effects of intravaginal oestradiol - 3: 17β on the cell structure of the vaginal epithelium of the ovariectomized mouse

The ultrastructure of the vaginal epithelium of the ovariectomized mouse, was studied after oestradiol treatment. Tissue for electron microscopy was fixed at various times after injection in 2% osmium tetroxide and embedded in "Araldite". The earliest change seen in the vaginal epithelium after the intravaginal application of oestradiol occurred in nucleolar structure. In untreated animals nucleoli were small and of relatively uniform texture. After local application of oestradiol they increased in size and changed in appearance due to the development of large deeply staining intranucleolar bodies. The response became evident 1 hr after application and reached a maximum at 2-5 hr. Nucleoli from treated animals retained this structure up to the latest time of study (20 hr). Changes were also observed in mitochondrial number, cell and nuclear size, but these changes were small and inconsistent and occurred only at the later times. The significance of these results is discussed in relation to the action of oestradiol.