LUTEINIZING HORMONE-ENHANCED INVITRO MATURATION OF BOVINE OOCYTES WITH AND WITHOUT PROTEIN SUPPLEMENTATION

Luteinizing hormone was shown to enhance maturation of immature oocytes obtained from slaughtered cattle as reflected by elevated proportions of oocytes that fertilized and reached blastocyst stages in vitro after in vitro fertilization (IVF). Higher proportions of ova were fertilized in vitro after in vitro maturation (IVM) in modified TCM-199 (TCM-199 + BSA + LH [USDA-bLH-B5, 100 μg/ml]) than in TCM-199 alone (p < 0.01). Further improvement in IVF (p < 0.005) followed IVM when 20% proestrous (Day 20) bovine serum replaced the BSA, but similar proportions of inseminated ova (22.2% and 22.6%) developed into blastocysts. The positive LH effect was verified in defined conditions for IVM. Exposure of oocytes to the purified LH preparation (without any other added protein or biological substances) during IVM improved (39.7% in TCM-199 vs. 73.5% in TCM-199 + LH; p < 0.001) and blastocyst development (7.9% vs. 28.2%; p < 0.005), respectively. Efforts to better define effective concentrations of LH revealed no difference in viability after IVM with 50 μg LH/ml vs. 100 μg LH/ml (27.0% vs. 28.3%, respectively); 10 μg LH/ml did not enhance viability when compared to TCM-199 alone (10.8% vs. 9.9%). Results demonstrate potential utility of this approach for investigation of factors influencing mammalian development by specific effects initiated during the interval of oocyte maturation.