Effect of Obesity on Selected Reproductive Parameters in Female Sprague Dawley Rat (Rattus norvegicus) Model

Aims: To determine changes in frequency of occurrence and durations of estrous cycle stages and measure serum levels of cortisol and estradiol in Sprague Dawley rats.

Study Design: Laboratory Experimental research Design.

Place and Duration of Study: Department of Veterinary Anatomy and Physiology, Chiromo Campus, University of Nairobi Kenya, March to June 2017.

Methodology: Obesity was induced through a High Energy Diet (HED) after which frequency of occurrence and durations of estrous cycles stages, serum estradiol 17b and cortisol hormone levels were analyzed. Twenty four, three-month-old sexually mature female Sprague Dawley rats grouped into replicates of six rats were fed either on HED (n=12) or a control diet (n=12) for seven weeks after which 12 obese rats and 12 controls were evaluated for estrous cycles durations and frequency of occurrence through vaginal smears. Six rats from control and obese groups then underwent cervical dislocation followed by collection of blood through cardiac puncture. This was followed by analysis of serum cortisol and estradiol 17b hormone levels using ELISA technique, Mean values of estrous cycle stages’ frequencies of occurrence, serum levels of cortisol and estradiol were subjected to Student t-test to evaluate any significant differences at P=.05.

Results: Obese rats had disrupted and extended estrous cycle stages, elevated serum cortisol (5.12±1.45) and estradiol (214±17.28) levels. Student t-test analysis indicated significant differences between means of frequencies of occurrence of proestrus (t=-2.66, P=.02) estrus (t=5.13, P=.00) and diestrus (t=-2.45, P=.02) stages as well as serum levels of cortisol (-2.87, P=.04) and estradiol 17b (t=5.37, P=.00). There was an inverse correlation between concentrations of cortisol and estradiol in blood sera of obese rats:-r =0.64.

Conclusion: Obesity leads to an inverse relationship between estradiol and cortisol resulting to disruption in the rat’s estrous cycles.