A Comparative Study of Steroid Hormone Levels and Oestrogen Receptor alpha (ERα) between Normal Bitch Uteri and Pyometra during Dioestrus

Abstract

Ovarian steroid hormones and their receptors play an important role in both physiological as well as pathological changes seen in the uterus. For the further understanding of the mechanism of pyometra, in relation to steroid hormones and their receptors in the bitch, the difference between the expression of the oestrogen receptor alpha (ERa) between normal and pyometra bitches during dioestrus was investigated. Uterine samples were collected during dioestrus from normal and pyometra bitches. Immunohistochemistry was used to investigate
the expression of ERa in the different compartments of the uterus. The results showed that the levels of steroid hormones in the normal and the pyometra group were similar, while ERa staining scores were significantly lower in the epithelia of the pyometra group compared to the normal group. This suggested that the expression of ER in the epithelia was strongly downregulated in pyometra cases compared to normal uteri during dioestrus. The mechanism of this downregulation may be due to more prolonged levels of progesterone
and/or the suppression of oestrogen, via ERa, in order to enhance uterine infection. However, any differences of ERa localization in the stroma and the myometrium between normal uteri and pyometra was not obvious.