Changes in vaginal epithelium are known to occur during the normal
oestrous or menstrual cycle and in
ovariectomised animals in response to various hormones. However, vaginal
changes due to exogenous
gonadotrophins superimposed on the normal hormonal milieu as occurs in
in vitro fertilisation programmes
have not previously been demonstrated. Female rats were hyperstimulated
with follicle stimulating hormone
and human chorionic gonadotrophin prior to mating. Control mated animals
were not injected. Vaginal
tissue was collected at 4.5, 5.5 and 6.5 d after mating. Tissue was processed
for light microscopy.
Hyperstimulation by the exogenous gonadotrophins caused mucification, a
decrease in the number of
epithelial layers and an increase in the thickness of the epithelium on
d 4.5 of pregnancy. The mitotic index
of the epithelial cells was depressed in the hyperstimulated rats with
respect to control animals. Exposure to
high levels of oestradiol and an altered progesterone[ratio ]oestradiol
ratio appear to have caused the changes in
the vaginal epithelium.