EFFECTS OF GROWTH-HORMONE, ACTIVIN, AND FOLLISTATIN ON THE DEVELOPMENT OF PREANTRAL FOLLICLE FROM IMMATURE FEMALE MICE

The aim of this study was to investigate whether GH and insulin-like g rowth factor I (IGF-I) are involved in preantral folliculogenesis and, if so, to clarify the relationship between GH/IGF-I and activin/ foll istatin (FS) systems in immature female mice. Ovaries were obtained fr om 11-day-old mice, and preantral follicles, 100-105 mu m in diameter, were mechanically isolated and selected for culture. Ten preantral fo llicles per well were cultured with different quantities and combinati ons of additives as follows: no additives (control), recombinant human FSH (rhFSH), IGF-I, recombinant human GH (rhGH), activin A, and recom binant human FS (rhFS). Mean diameters of the follicles were measured daily, and estradiol and immunoreactive inhibin levels in the cultured medium were assayed by RIA on day 4. rhGH showed stimulatory effects on the follicular diameter and the secretion of estradiol and immunore active inhibin. These effects were augmented by the presence of IGF-I and activin A. IGF-I alone did not show any stimulatory effect. The ad dition of rhFSH to activin A or to rhGH and activin A promoted preantr al follicular growth and hormone production. On the other hand, GH-or activin-stimulated follicular growth was suppressed by rhFS in a dose- dependent manner. These results indicate that activin A and rhGH may p lay an important role in controlling earlier phases of follicular deve lopment during the infantile period, which is considered to be gonadot ropin independent.