Pre-pubertal exposure to high temperature impairs ovarian and adrenal gland function in female rats

The influence of different levels of heat exposure on the functions of ovarian and adrenal gland were investigated in pre-puberty female rats. Three-week old female rats were treated with control (26°C) or three higher temperatures (38, 40 and 42°C) for 2hr/day. After 9 days of treatment, blood samples were collected for measurement of luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol-17β, corticosterone, cholesterol and triglyceride. Adrenal glands, ovaries and liver were collected for analyzing gene expressions. Body and liver weight were significantly low in the 42°C heating group. Circulating LH and triglyceride in the 42°C heating group were significantly lower, and estradiol-17β, corticosterone and cholesterol were significantly higher than those of the control group. The gene expression of 3β-HSD and P450c21 in the adrenal gland; 3β-HSD, receptors of LH, FSH and estrogen in the ovary were significantly low in heated rats. The liver gene expressions of caspase 3 and NK-κB were significantly high in 42°C heated rats, suggesting that the ability of liver metabolic function reduced in the 42°C heated rats. These results demonstrated that the high temperature is responsible for suppression of ovarian function by decreasing the expression of steroidogenic enzymes, estrogen and gonadotropin receptors in the ovary. Increase in circulating estradiol-17β in the heated rats may be due to accumulate this hormone in circulation by potential changes in liver metabolism during the heat stress.