Oocyte growth in the immature rat.

Growth rates of oocytes in the ovary cannot be measured directly. However, oocyte growth can be determined by relating oocyte diameter to the time the enclosing follicle has been growing, calculated from kinetic studies of granulosa cell doubling time. For the ovaries of immature rats aged 16 and 28 days, oocyte diameter platted against time gave straight and parallel lines, showing that the diameter is positively and linearly related to time and that oocytes grow at the same rate at both ages. However, during earliest developmental stages (type 3a follicles with 10-20 granulosa cells) the growth rates differed, being faster at 16 days and slower at 28 days than at later stages.