Follicles explanted from pentobarbitone-treated rats provide a model for atresia

Graafian follicles from rats treated for 1 or 2 days with pentobarbitone sodium (Nembutal) were similar in appearance to pro-oestrous preovulatory follicles, but after 3 or 4 days of treatment early atretic changes were recognized. Ovulatory efficiency decreased to 88, 70, 52 and 31% after 1, 2, 3 and 4 days of treatment, respectively. The mean +/- s.e.m. rate of accumulation (ng/follicle/24 h) of progesterone, androstenedione and oestradiol was 3.6 +/- 0.7, 4.0 +/- 0.3 and 18.9 +/- 3.9 respectively in preovulatory follicles and 10.2 + 1.7, 0.9 +/- 0.1 and 1.9 +/- 0.4 respectively in follicles explanted from rats treated for 4 days with Nembutal. Addition of LH (5 micrograms/ml) to the culture medium stimulated steroid accumulation by both types of follicles. Thus atretic follicles are characterized by impaired androgen and oestradiol formation. Addition of testosterone (1 microgram/ml) to the culture medium increased the accumulation of oestradiol by atretic follicles. It is inferred that the early stages of atresia of rat follicles are distinguished by a deficiency in the activity of enzymes responsible for the conversion of progesterone to androgens that can serve as substrates for aromatization.