Induction of polycystic ovary by testosterone in immature female rats: Modulation of apoptosis and attenuation of glucose/insulin ratio

Polycystic ovarian syndrome is seen in 5% of fertile aged women. However, there is no satisfactory PCOS model in experimental animals. To induce polycystic ovary phenotype in immature female rats, Wistar rats 21 days of age were injected daily with testosterone propionate I mg/100 g body weight dissolved in propylene glycol or propylene glycol for up to 35 days. Seven days of injection with testosterone (T) resulted in the appearance of large cystic follicles and a dramatic accumulation of multi-layer preantral follicles. At 42 days of age puberty in control animals was evident by the appearance of corpora lutea. In contrast in T treated animals no corpora lutea formation was seen even at the age of 56 days. Progesterone in the control animals was elevated at the age of 42 days in contrast with the T treated animals in which progesterone remained low (20% of control). While during 14 days of T injection most of the follicles did not have progressive apoptosis, at 21-35 days of injection (42-56 days of age) the vast majority of follicles became apoptotic. Progressive degeneration of oocytes was evident in T treated animals reaching 70-85% of total oocytes at 21-35 days of T injection compared to 30-40% in control animals. Western blot analysis of ovarian homogenates revealed gradual decrease in BCL-2 content, evident at 28 and 35 days of T injection compared to control animals. Interestingly, the fasting glucose/ insulin ratio was dramatically reduced in T treated animals following 14 days of testosterone treatment compared to controls. Our data suggest that T injection to immature female rats can induce polycystic ovaries, block ovulation and attenuate progesterone production. Moreover, normal/low glucose and high insulin blood levels in the testosterone treated rats raises the possibility that elevated androgens can lead to insulin resistance in this experimental PCOS model.