Systemic treatment in the rat with epidermal growth factor causes polycystic growth of the ovaries

Background: It has previously been suggested that epidermal growth factor (EGF) plays a role in the function of the ovary. We administered systemic EGF to assess the influence of EGF receptor stimulation on the morphology of the ovaries. Methods: Forty-eight female Wistar rats were allocated to five groups receiving EGF treatment (150 mu g/kg/day) for 0 (controls), 1, 2, 3 and 4 weeks. All rats were exactly 8 weeks at the start of the experiment and 12 weeks at sacrifice. The EGF was administered in the weeks prior to sacrifice. At sacrifice, the perfusion-fixed ovaries were removed and weighed, and the volumes of tissue components were quantified using stereology. Results: EGF administration increased the total weight of the ovaries from 129+/-18 mg in the controls to 158+/-29 mg (p<0.05) after one week. In subsequent weeks the total weight increased to 230+/-73 mg (p<0.001). The weight gain after one week of treatment was exclusively due to a fourfold increase in follicular cyst volume (p<0.01). In subsequent weeks the cyst volume was increased up to eightfold. After 2, 3 and 4 weeks of treatment the quantity of luteinizing cells was likewise increased by 70% (p<0.01). Conclusion: EGF administration causes the follicular cells to produce cysts and increases the quantity of luteinizing cells.