Ovarian development in hypopituitary Snell dwarf mice. The size and composition of the follicle population

The size and composition of the follicle population in the ovaries of sterile Snell dwarf ( dw/dw ) strain mice differ from that in phenorypically normal contemporaries from 21 days of age onwards. The number of small (primordial) and growing follicles in the ovaries of dwarfs and phenotypically normal contemporaries was not statistically different during the infant and juvenile periods. At 21 days of age, ovaries from dwarf mice contained significantly more primordial follicles due to a reduction in the rate of atresia in the nongrowing pool of oocytes. This difference was maintained throughout the adult period studied. The dwarf mice used in this study did not ovulate. Nevertheless, antral follicles were present and the developmental sequence of follicular growth followed that of controls. From 92 to 432 days of age, however, the total number of growing follicles was reduced in dwarfs. Furthermore, specific compartments of the growing follicular population were affected much earlier. These data are discussed in relation to the reportedly normal concentrations of follicle stimulating hormone and luteinizing hormone and the reduced concentrations of prolactin and growth hormone in the pituitary gland and blood plasma of the dwarf female.