361 EFFECT OF HORMONES, EGF AND β-MERCAPTOETHANOL ON IN VITRO MATURATION OF CAPRINE OOCYTES

Abstract

In vitro maturation of oocytes is an integral part of in vitro culture system. In almost all studies of mammalian in vitro maturation, the basic medium is supplemented with serum and hormones. The maturation medium and selection of protein supplements, growth factors, antioxidants and hormones for IVM play an important role in subsequent in vitro fertilization and in vitro embryo development. The objective of the present experiment was to study the effect of exogenous addition of hormones, epidermal growth factor, insulin and β-mercaptoethanol to the maturation medium for in vitro maturation of caprine oocytes. A total of 1540 oocytes were collected from slaughtered goat of 1.5 to 2.5 year of age and randomly divided in to treatment groups. Group 1; COCs were matured in TCM-199 medium containing 10% calf serum (NCS) and 3 mg mL^-1 BSA (used as a base medium) for control, Group 2; COCs were matured in a base medium supplemented with hormones (5 μg mL^-1 FSH, 5 μg mL^-1 LH and 1 μg mL^-1 estradiol-17β), Group 3β COCs were matured in a base medium supplemented with 50 ng mL^-1 insulin, Group 4β COCs were matured in a base medium supplemented with hormones and 10 ng mL^-1 EGF, Group 5; COCs were matured in a base medium supplemented with hormones and 50 mM β-mercaptoethanol and Group 6; COCs were matured in a base medium supplemented with hormones and 50 ng mL^-1 insulin. These COCs were matured at 38.5°C in 5% CO² in air for 27 h. After the maturation, oocytes were separated from cumulus and corona cells by treatment with 0.1% hyaluronidase and by passing through a fine pipette. They are them fixed in 2.5% glutaraldehyde, stained with DAPI and observed under fluorescent microscope for evidence of nuclear maturation. The maturation rates in groups 1 to 6 were 33.6%, 38.0%, 39.7%, 60.0%, 37.4%, and 44%, respectively. Statistical analysis (ANOVA) after arcsin transformation revealed that the maturation rate in group 4 was statistically significant (P < 0.05) as compared to those in groups 1, 2, 3, 5, and 6. The results suggest that the supplementation of EGF in maturation medium significantly enhances the in vitro maturation rate of caprine oocytes.