Follicle Growth in the Immature Rat Ovary

Abstract

In ovaries of immature rats the following parameters were estimated from autoradiographs prepared after pulse labelling with tritiated thymidine: 1) The time it takes follicles to grow from one stage of development to another. This could be derived from the total number of granulosa cells in these stages and from their doubling times. The doubling time of granulosa cells was determined from their labelling index and the duration of their DNA-synthesis phase.2) The number of follicles present in the ovary at different ages.3) The number of follicles, which start on their development at different ages.It was found, that more follicles start to grow in 8 and 16 days old rats (2.0/h) than in 28 days old ones (1.0/h). Moreover, the follicles grow somewhat faster earlier in life than later. The development from a follicle with one layer of granulosa cells to one with several layers and antrum formation takes about 15 days in the first half of the period of immaturity while it takes about 17 days as the animal approaches maturity. Pedersen (1969Pedersen ( , 1970aPedersen ( ,«, 1972 introduced granulosa cell kinetics, using [3H]-thymidine ([;iH]T), to time follicle growth. His studies in mice indicated that the time it takes a 3 b follicle (20 granulosa cells in the largest cross section) to develop to an antral one changes with age and is about 16 days in the 21 days old mouse. So far, follicle growth rates in the rat, the species in which the reproductive system has been studied most extensively, have not been determined. Therefore, 375

Oocyte growth in the immature rat

“…The times that follicles take to pass through successive stages of development have been calculated for the immature rat (Hage et al, 1978) and it is therefore possible to determine the time pattern of oocyte growth by relating oocyte diameters to these times. (Pedersen, 1969) (Hage et al, 1978 -fig. 1), a phase of fast oocyte growth and a phase of apparently arrested growth can be distinguished.…”

“…Follicle development between birth and first ovulation has been investigated by studying granulosa cell kinetics in ovaries of mice (Pedersen, 1969) and rats (Hage, Groen-Klevant & Welschen, 1978), and in this way the growth rates of different types of follicles (as defined by Pedersen & Peters, 1968) have been established.…”

“…Thus, a biphasic pattern has been found in the mouse (Brambell, 1928;Moore & Lintern-Moore, 1974;Lintern-Moore & Pantelouris, 1975, rat (Mandi & Zuckerman, 1952;Brambell, 1956) and all other mammals studied (Brambell, 1956). However, since it has been demonstrated that large follicles grow faster than medium ones (Pedersen, 1969;Hage et al, 1978), the question arises whether the biphasic pattern of the relationship between oocyte diameter and follicle diameter is caused by changes in follicle growth, oocyte growth, or both. It seemed possible to determine growth rates of oocytes indirectly, using data on growth rates of follicles.…”

Growth of Primordial Oocytes in Neonatal and Adult Mammals

“…The faster development of primordial follicles in younger mammals than in older ones is not limited to the xenograft situation. Faster development of follicles in younger rats has been reported in an autoradiographic study [29]. In mice and rats, follicle development begins within a few days of birth, and antral follicles appear during the third week post partum, whereas follicle development in adults is estimated to take around 2 months [4].…”

From the germinal cells to the newborn animal: The transmission of genes and life through the generations

“…The first one, the 'basal' growth concerns follicles, from the primordial stage till the preantral stage (Hage et al, 1978;Driancourt, 1991;Driancourt et al, 1991). This phase is mainly under paracrine control of growth factors (GF) (Peters et al, 1973).…”