EFFECT OF RECOMBINANT HUMAN GONADOTROPINS ON OOCYTE MEIOSIS AND STEROIDOGENESIS IN ISOLATED PREOVULATORY RAT FOLLICLES

In order to study the effects of recombinant human luteinizing hormone (LH) and recombinant follicle stimulating hormone (FSH) on the pre-ov ulatory follicle, immature pregnant mare's serum gonadotrophin-treated rats were used. Follicles were isolated by dissection and incubated f or 4 h in medium 199 containing different concentrations of the gonado trophins. In control medium the follicle-enclosed oocytes remained arr ested in prophase I, but in the presence of recombinant human LH or re combinant human FSH, a concentration-dependent increase in the proport ion of oocytes which underwent germinal vesicle breakdown (GVB) was se en. The lowest effective concentration of recombinant human LH was 10- 50 ng/ml, and at 1000 ng/ml 97% of the oocytes underwent GVB. Recombin ant human FSH was also effective, albeit slightly less so than recombi nant human LH. Follicular oestradiol accumulation was stimulated up to 5-fold, both gonadotrophins showing similar effectiveness. Follicular progesterone and testosterone accumulation was markedly stimulated by recombinant human LH, giving a maximal 20-fold and 15-fold increase r espectively. A 5-fold stimulation of progesterone production was found with recombinant human FSH. When submaximal concentrations of recombi nant human LH and recombinant human FSH were combined, an additive eff ect was found on oocyte meiosis and on oestradiol and progesterone acc umulation. The results are in agreement with previous studies using pi tuitary gonadotrophin and show that both recombinant human LH and reco mbinant human FSH have intrinsic effects on oocyte meiosis and steroid ogenesis. It is likely that in the physiological situation in vivo, bo th gonadotrophins contribute to regulate these events in the peri-ovul atory period.