Changes in DNA, cyclic nucleotides and steroids during induced follicular atresia in the hamster

Atresia was induced in antral follicles of hypophysectomized PMSG (30 i.u.)-treated hamsters by an i.p. injection of PMSG antiserum. Mature antral follicles were isolated and incubated for 1 h. When expressed per follicle, cAMP increased 108% above control levels at 2 h, while cGMP rose 117% at 4 h; both nucleotides then declined (12-72 h). DNA per follicle fell below control values by 24 h and reached its lowest point at 48 h. Serum concentrations of oestradiol-17 beta and testosterone were 50% lower by 1 h after injections of PMSG antiserum. Oestradiol and testosterone in serum, incubation medium and tissue dropped rapidly to reach basal values by 12 h. Serum progesterone showed a sharp increase at 4 h then dropped below control levels by 12 h and remained constant thereafter. In tissue and medium, progesterone rose to peak values at 8 h, then dropped to control levels with no significant changes for the remaining 64 h. The precipitous decreases in both oestradiol and testosterone in the serum, medium and tissue indicate inhibition of steroid synthesis at some point after progesterone formation. These results demonstrate the usefulness of this model for following atretic changes in a synchronized population of Graafian follicles.