Hwang, W S; Cha, K Y; Park, S E; Ko, J J; Chung, H M; Lee, E S; Lee, B C; Lim, J M
Abstract:
This study was conducted to examine the effects of carbohydrates and aminoacids on the maturation and fertilization of bovine oocytes. To evaluate theeffect of each treatment without any unpredictable interference, oocytes werecultured in a simply defined medium (modified Tyrode’s medium; mT)without the addition of hormones and proteins. In Experiment 1, oocytematuration to the metaphase-II stage was significantly(P<0.0001) enhanced after the addition of glucose(5.6 mм), lactate (10 mм) and/or pyruvate (0.5 mм) to mT(37-74%) than after no addition (0%). In mT supplementedwith glucose, the addition of 19 essential and non-essential amino acids (aa;0, 0.01, 0.1, 1, 5 or 10%) did not further improvein vitro maturation (Experiment 2) orin vitro fertilization (Experiment 3) of oocytes.However, more (P<0.05) pronuclear formation after invitro-insemination was found in oocytes matured in mT with 1% aa andglucose than in oocytes matured in mT with glucose alone (56% vs.35%). Penetration of spermatozoa into the ooplasm was initiated at 3 hafter insemination and pronuclear formation from 8 h (Experiment 4). Whencultured inseminated oocytes were examined up to 192 h post insemination, asignificant (P<0.05) increase in the number of 2-cell(18 v. 38%) and 8-cell embryos, (7v. 20%) and morulae (0 v.8%) was found after the addition of 1% aa to mT with glucosethan after no addition (Experiment 5). A limited number of oocytes matured inmT with aa and glucose developed to the blastocyst stage (6%). Theseresults indicate that exogenous carbohydrates and amino acids areprerequisites for the maturation and fertilization of bovine oocytesin vitro. Glucose alone promotes the nuclear maturationof oocytes, whereas amino acids aid the pronuclear formation of fertilizedoocytes.