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

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Abstract
Graafian follicles from rats treated for 1 or 2 days with pentobarbitone sodium (Nembutal) were similar in appearance to pro-estrous 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 .+-. standard error of the mean rate of accumulation (ng/follicle per 24 h) of progesterone, androstenedione and estradiol 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. Lutropin addition (5 .mu.g/ml) to the culture medium stimulated steroid accumulation by both types of follicles. Thus atretic follicles are characterized by impaired androgen and estradiol formation. Testosterone addition (1 .mu.g/ml) to the culture medium increased the accumulation of estradiol by atretic follicles. Apparently 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.