Introduction:
Aim: The aim of the study was to identify the morphological features of brown adipose tissue in an experimental model of PCOS under intermittent cold exposure.

Material and Methods:
The study was conducted on 40 immature female WAG rats, aged 27 days and weighing 80-90 g, which were divided into five groups (eight animals per group). Group 1 consisted of intact rats. Group 2 included rats that received daily subcutaneous injections of 0.2 ml of purified and sterilized olive oil for 25 days. Group 3 consisted of rats subjected to intermittent cold exposure for 25 days. Group 4 included rats in which dehydroepiandrosterone (DHEA)-induced PCOS was modeled. Group 5 consisted of rats that, in addition to intermittent cold exposure, received DHEA administration. Rats in groups 1-5 were removed from the experiment on day 26 by cervical dislocation. The material for morphological study was brown adipose tissue, which was cut from the interscapular region during the autopsy of animals. Histological, morphometric and statistical research methods were used.

Results:
During the survey microscopy of the slides stained with hematoxylin and eosin, brown adipose tissue from the interscapular region of rats in all groups was characterized by the presence of parenchyma and stroma. Depending on the number of lipid droplets, all adipocytes were classified into three categories: adipocytes containing up to 5 lipid droplets (type 1 adipocytes); adipocytes containing 5-10 lipid droplets (type 2 adipocytes); and adipocytes containing more than 10 lipid droplets (type 3 adipocytes). Brown adipose tissue in DHEA- induced PCOS was characterized by a decrease in the number of type 3 adipocytes and an increase in the number of type 1 adipocytes; a reduction in adipocyte area, and an increase in adipocyte nuclear area. Under intermittent cold exposure and during DHEA administration combined with intermittent cold exposure, brown adipose tissue was characterized by a decrease in the number of type 2 and 3 adipocytes and an increase in the number of type 1 adipocytes; a reduction in adipocyte area; an increase in adipocyte nuclear area; and an increase in the number of blood vessels in the stroma.

Conclusions:
In DHEA-induced PCOS, under intermittent cold exposure, and during DHEA administration combined with intermittent cold exposure, activation of brown adipose tissue in the interscapular region is observed, with the degree of activation being minimally, moderately, and maximally expressed, respectively.