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

Abstract

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.

Integrative Analysis of Vaginal Microorganisms and Serum Metabolomics in Rats With Estrous Cycle Disorder Induced by Long-Term Heat Exposure Based on 16S rDNA Gene Sequencing and LC/MS-Based Metabolomics

“…Therefore, it is suggested that L-arginine might reduce the disorder of the estrous cycle in rats by regulating glucose and lipid metabolism and amino acid synthesis during HE. Studies have shown that high temperature inhibits ovarian function and reduces the follicular growth rate ( Zheng et al, 2019 ). As a potential endocrine disruptor with estrogenic activity, the phthalic acid mono-2-ethylhexyl ester may inhibit follicular growth through the oxidative stress pathway ( Zhang et al, 2018 ) and by reducing estradiol production ( Wang et al, 2012 ).…”

“…The experimental animals were fed in cages for 2 days, followed by vaginal cytological smears at the same time each morning and evening. A total of 44 rats were randomly divided into two groups (with regular estrous cycles): (1) control group (C group)—the animals were fed under standard temperature and humidity conditions; and (2) HE group (H group)—each model animal was exposed to heat (38°C ± 0.5°C; relative humidity 55% ± 5%) for 2 h/day (9:00–11:00) in a small-animal heat chamber ( Zheng et al, 2019 ; An et al, 2020 ). The experiment lasted for at least 90 days with free access to food and water.…”

Pathophysiological Changes in Female Rats with Estrous Cycle Disorder Induced by Long-Term Heat Stress

“…It is not suitable for the further study of the human menstrual cycle. There are few studies on heat stress in female rats, and the modeling conditions are different, and the conclusions are inconsistent [1,4,13,14]. Herein, we proposed a 90-day heat stress model to redefine the temperature, duration, and frequency of heat exposure and established a stable and effective rat estrus cycle disorder model on the premise of no heatstroke.…”

Understanding how environmental factors influence reproductive aspects of wild myomorphic and hystricomorphic rodents

“…The degeneration of ovarian tissue and reduction in folliculogenesis and oogenesis were also observed as responses to thermal injury in females ( Zheng et al, 2019 ). In prepubertal female Wistar rats, Zheng et al (2019) observed the ovarian function of these animals in the face of thermal stress at different temperatures (38, 40, and 42 °C for 2 h/ day). The plasma levels of LH and triglycerides and the expression of LH receptors FSH and estradiol-17β in the ovaries were significantly lower at higher temperatures (especially at 42 °C) than in the control (26 °C).…”