An autoradiographic study of follicle growth in the ovaries of cyclic rats.

Follicle growth in the ovaries of cyclic rats was studied by autoradiography after pulse labelling with [3H]thymidine: growth rates and numbers were determined for follicles of the types 3b to 6 (type 3b: follicles with 1-2 layers of granulosa cells; type 6: follicles with a diameter of 200 microns and usually with a single antrum). The data indicate a total time of follicle development, from type 3b to ovulation, of 22 days. Growth of follicles of the types 3b to 6 in these cyclic rats was roughly similar to that in late prepubertal animals, previously studied. However, some changes of the growth of these types of follicles, related to the stages of the cycle, could be noted.