Our objective was to determine if replacing glucose with fructose would decrease cytoplasmic lipid accumulation during culture of embryos with or without regulators of metabolism. In vitro-produced bovine zygotes were cultured 60 hr in chemically defined medium-1 (CDM-1) plus 0.5% BSA and 0.5 mM fructose or glucose in Experiment 1, and glucose in Experiment 2. In both experiments, 8-cell embryos were next cultured 135 hr in CDM-2 plus 2 mM fructose or glucose in factorial combination with five treatments: (Experiment 1: control, 10% fetal calf serum (FCS), 0.3 microM phenazine ethosulfate (PES), 30 microM dinitrophenol (DNP), and PES + DNP), and (Experiment 2: control, PES, PES + DNP, and 1 and 3 microg/ml cerulenin (C1 and C3)). Day 7.5 blastocysts were stained with Sudan Black B to quantify cytoplasmic lipid droplets as small (SD, <2 microm), medium (MD, 2-6 microm), or large (LD, >6 microm). Blastocyst rates per oocyte were 22% (Experiment 1) and 15% (Experiment 2) higher (P < 0.05) for fructose than glucose. For Experiment 1, numbers of MD were lower for PES, DNP, and PES + DNP than control and FCS (P < 0.05). LD were lower for PES and DNP than control, and higher for FCS than all other treatments (P < 0.05). For Experiment 2, MD were lower (P < 0.05) for PES, and PES + DNP than C1, C3, and control. For LD, PES was lower (P < 0.05) than control, C1, and C3, but not different from PES + DNP. The only effect of hexose on lipids was that fructose resulted in fewer MD (P < 0.01) in Experiment 2. In conclusion, fructose produced more blastocysts than glucose, and PES reduced lipid accumulation.
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