Glucose metabolism by preimplantation pig embryos

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Abstract
Pig embryos were collected, 2-7 days after oestrus, in modified BMOC-2 containing glucose as the only energy source. Embryos were incubated individually in medium containing [5-3H]-, [1-14C]- or [6-14C]glucose. Total glucose metabolism, as measured by [5-3H]glucose use, increased steadily from the 1-cell to the 8-cell stage. Total glucose use increased (P < 0.05) at the compacted morula stage and was highest (P < 0.05) at the blastocyst stage. Production of 14CO2 from embryos metabolizing [1-14C]glucose increased steadily from the unfertilized ovum to the 8-cell stage. Metabolism of [1-14C]glucose increased at the compacted morula stage (P < 0.05) and continued to increase (P < 0.05) to the blastocyst stage. Metabolism of [6-14C]glucose increased steadily from the unfertilized ovum to the compacted morula stage. Metabolism of [6-14C]glucose was highest (P < 0.05) for the blastocyst stage. Percentage pentose phosphate pathway activity of total glucose metabolism before the 4-cell stage was higher (> 5%) than that of 8-cell to blastocyst stage embryos (.apprx. 1%). When embryo metabolism was determined on a per cell basis for each isotope, the compacted morulae stage (16 cells) had a higher total glucose metabolism than all other embryo stages (P < 0.05), while early blastocyst (32 cells) and blastocyte (64 cells) stage embryos metabolized more [5-3H]glucose than all stages except compacted morulae (P < 0.05). Metabolism of [1-14C]glucose was highest for 1-cell embryos (P < 0.05), while there were no differences in [6-14C]glucose metabolism among stages of development (P > 0.05) on a per cell basis. The results indicate that glucose is not being metabolized readily by pig embryos before the 8-cell stage and glucose is utilized in higher amounts in embryos between the compacted morula and blatocyst stages. This is the first report of glucose metabolism and determination of pentose phosphate pathway activity in pig embryos.