Steroid-level response to insulin-like growth factor-1 in oocytes matured in vitro.
The objective was to establish the influence of insulin-like growth factor-1 (IGF-1) on steroid production and nuclear maturation during oocyte in vitro maturation (IVM). Immature-selected rabbit follicular oocytes, divided as cumulus-oocyte complexes (COC) and denuded oocytes (DO), were cultured in Brackett's medium with different concentrations of IGF-1 at 0, 50, 100 and 200 ng/ml. After 8 and 16 h of culture, the oocytes were assessed for nuclear maturation by acetic-orcein stain, and media were analyzed by enzyme-immunoassay (EIA) for 17 beta-estradiol (E), progesterone (P), androstenedione (A) and testosterone (T) content. After culture treatments with IGF-1 significantly increased (P < 0.01) the incidence of nuclear activation (germinal vesicle breakdown stage, GVBD) and nuclear maturation (metaphase II stage); maximum stimulation occurred at 100 ng IGF-1/ml (86.9 vs. 49.3% in control). Compared to controls, the presence of IGF-1 in cultures was associated with a significant increase of E and A production by COCs (P < 0.01). However, P and T levels were not significantly influenced by the IGF-1. In addition, positive correlations between E/T and E/A ratios and nuclear maturation rates were only found in the IGF-1 treatments. Regarding the DOs, neither positive effects in nuclear maturation rates nor increase of steroid levels in culture were observed for any treatment. These results suggest that: (1) IGF-1 had a significant effect on E and A production during oocyte maturation; (2) the addition of IGF-1 enhanced nuclear maturation significantly in rabbit oocytes; and (3) all these effects are only possible in oocytes surrounded by cumulus cells.
Lorenzo
P L
PL
Departamento de Fisiología Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Spain. lorenzopl@vet.ucm.es
Illera
J C
JC
Silván
G
G
Munro
C J
CJ
Illera
M J
MJ
Illera
M
M
D000735:Androstenedione / Q000096:biosynthesis; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects*; D002478:Cells, Cultured; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D006728:Hormones / Q000096:biosynthesis; D007124:Immunoenzyme Techniques; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009865:Oocytes / Q000166:cytology / Q000187:drug effects*; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects; D011374:Progesterone / Q000096:biosynthesis; D011817:Rabbits; D013256:Steroids / Q000096:biosynthesis*; D013739:Testosterone / Q000096:biosynthesis
D006728:Hormones; D013256:Steroids; D013739:Testosterone; D000735:Androstenedione; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I