[The influence of follicular factors on the in vitro maturation of bovine oocytes].

Immature oocytes from antral follicles of cattle were tested for the effect of follicular factors on maturation. In vitro maturation was accomplished by use of follicular fluid from small (2--5 mm) and large (above 15 mm) follicles and by addition to the medium of a granulose factor (GF) which had been isolated from the surface of granulosa cells. The parent material, with 84% (72/86) of oocytes at the germinal vesicle stage (GV-S) at the beginning of culturing, could be rated immature. 46% of all oocytes (41/89) had reached telophase I or metaphase II (full maturation) after 24 hours of maturation in hormone-free control medium (TCM 199 + 10% of foetal calf serum). 36% of oocytes (53/84), on the other hand, stayed between GV breakdown (GVBD) and anaphase I (incipient maturation). Full maturation was reached by as little as 14%. GF and follicular fluid from small antral follicles were found to inhibit GVBD in the oocytes. 59% (36/61) or 48% (61/127) of oocytes were blocked at GV stage. Positive determination of maturation inhibiting action of the above follicular components may provide a chance for their target-oriented use in control of the maturation process. The pool of immature oocytes of the ovaries, under such circumstances, might be more systematically utilised for in vitro manipulations.