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Summary. Three stages of follicular atresia have been defined in the juvenile mouse ovary. Using autoradiography, the development and duration of the atretic process has been determined. The three stages of atresia represent consecutive stages in a single atretic process. A large follicle will incorporate 3Hthymidine into its granulosa cells: the labelling index of such a follicle is about 40%. As atresia sets in and progresses, the labelling index of the granulosa cells changes. This change was followed in autoradiographs prepared at different times after pulse labelling. Follicles in the early stages of atresia a day after label injection showed a higher labelling index than healthy follicles. This apparently paradoxical behaviour seems to result from a re-utilization of DNA freed by fragmented, pyknotic granulosa cells released into the follicular cavity. Labelling curves of follicles at different stages of atresia in relation to time were prepared. A comparison of such curves suggests that the time it takes a large follicle to become atretic is about 4 days.
Anne Grete Byskov (Mon,) studied this question.