The cell population kinetics of the ovary in 28-day-old mice were investigated. A method to determine growth rates of follicles is described, and the results obtained are discussed.
The granulosa cells in each follicle were considered to represent a single cell population. The time taken to double such a cell population was calculated from the labelling index of the granulosa cells and the duration of the synthesis phase of the single cells. Both parameters have been determined in autoradiographs prepared at different time intervals after the injection of tritiated thymidine.
Different stages of follicle development were classified according to the number of their granulosa cells. The actual time taken to grow to different stages was calculated from the time taken to double the number of the granulosa cells in these stages. It was shown that medium follicles grow at a slower rate than large follicles. A small follicle with one layer of granulosa cells took 16 days to develop into a large one with several layers and antrum formation.