24The purpose of this study was to compare the expression of 3β-hydroxystreroid 25 dehydrogenase (3β-HSD) in the uterus and ovary of healthy dogs and those with cystic 26 endometrial hyperplasia/pyometra complex (CEH-pyometra). Eighteen female dogs were 27 included in the study. Eleven bitches with open cervix CEH-pyometra were included in the 28 CEH-pyometra group and 7 diestrus bitches in the control group. For immunostaining a rabbit 29 polyclonal one raised against recombinant human type 2 (adrenal/gonadal) 3β-HSD was used.