Follicle-stimulating hormone and growth hormone act differently on nuclear maturation while both enhance developmental competence of in vitro matured bovine oocytes

摘要

To study the effect of FSH on nuclear maturation of in vitro-matured cattle oocytes, cumulus oocyte complexes (COC) were cultured in the presence or absence (controls) of FSH (0.05 IU/ml). The nuclear stage of the oocytes was assessed using 4,6-diamino-2-phenyl-indole staining after 16, 20 or 24 h of in vitro maturation and 18 h after the onset of fertilization. To assess the effect of FSH + growth hormone (GH) during in vitro maturation on the developmental capacity of oocytes, COC were incubatedin the presence of FSH (0.05 IU/ml), GH (100 ng/ml) or FSH + GH or without FSH or GH supplementation (controls) for 22 h, followed by in vitro fertilization and culture. To investigate whether FSH-induced oocyte maturation is exerted through the c-AMP pathway, cumulus oocyte complexes were cultured in M199 supplemented with FSH (0.05 IU/ml) and H-89 (10μM), a specific inhibitor of c-AMP-dependent protein kinase A. After 16 h of culture, the proportion of oocytes in metaphase II (MII) stage was determined. Cultures with GH and without FSH and H-89 served as controls. The percentage of MII oocytes after 16 h of incubation was lower in the presence of FSH than in controls (26 vs. 36; P<0.001); however, there was no difference between the 2 groups at 20 h, indicating a transient inhibition of nuclear maturation by FSH. Addition of GH increased the number of MII oocytes after 16 h of culture (P<0.001). The presence of FSH during in vitro maturation increased fertilization rate (87.6 vs. 78.6% in controls), cleavage rate and blastocyst development (P<0.001). GH increased cleavage rate and blastocyst development compared with controls (P<0.001); however, GH + FSH did not result in an additional increase in embryonic development compared with GH or FSH alone. The inhibition of nuclear maturation by FSH and its acceleration by GH were completely abolished by H-89. It is suggested that FSH retards nuclear maturation via a c-AMP-mediated pathway, and increases the fertilizability and developmental ability ofthe oocytes.