IN-VITRO MATURATION OF BOVINE OOCYTES IN THE PRESENCE OF GROWTH-HORMONE ACCELERATES NUCLEAR MATURATION AND PROMOTES SUBSEQUENT EMBRYONIC-DEVELOPMENT

Regulatory effect of GH on follicular growth and development in the co w is well documented. The aim of this study was to investigate the rol e of GH on in vitro bovine oocyte maturation. Therefore bovine cumulus oocyte complexes (COCs) were cultured in M199 without FCS and gonadot ropins and in the presence of 10, 100, or 1,000 ng/ml bovine GH (NIH-G H-B18). The COCs were incubated at 39 degrees C in a humidified atmosp here with 5% CO2 in air and nuclear stage was assessed after 2, 4, 8, 16, 22, and 24 hr of incubation using DAPI staining. To assess the eff ect of GH on developmental capacity of the oocytes, COCs were incubate d in the presence of GH for 22 hr, followed by IVF and in vitro embryo culture. Cultures without GH served as controls. For subsequent devel opment, the embryos were cultured in M199 supplemented with 10% FCS on a monolayer of BRL cells. Embryos were scored morphologically and the efficiency of the culture system was evaluated as (1) the percentage of cleaved embryos 4 days after IVF, (2) the percentage of blastocysts on day 9 expressed on the basis of the number of oocytes at the onset of culture, and (3) the percentage of hatched blastocysts on day 11 e xpressed on the basis of the total number of blastocysts present at da y 9. GH (100 and 1,000 ng/ml) significantly accelerated nuclear matura tion (P <0.001). At 4 and 8 h the percentage of oocytes in GV stage af ter GH treatment (54% and 19%) was significantly lower than the contro l (64% and 41%). Similarly at 16 and 22 h the percentage of oocytes in MII stage was significantly higher in the GH-treated group; (58% and 77%) and (46% and 62%) for GH and control respectively. The number of oocytes in MII beyond 22 hr of culture did not differ; 100 and 1,000 n g/ml GH induced significant cumulus expansion (P <0.05), which was not observed in the absence of GH. Addition of 100 and 1,000 ng/ml GH dur ing maturation significantly (P <0.01) enhanced subsequent cleavage ra te from (64% and 67%) in control to (75% and 81%) in GH-treated group; embryonic development in terms of day 9 blastocyst formation was also significantly increased in the presence of GH (29% and 34%) compared to the control (18% and 24%). The hatchability of the blastocysts was not influenced by GH. From the present data, it can be concluded that GH present during IVM has a beneficial effect on subsequent developmen t. (C) 1996 Wiley-Liss, Inc.