Oxidative utilization of glucose, acetate and lactate by early preimplantation sheep, mouse and cattle embryos

The production of radiolabelled CO2 from [U-14C]glucose, [1-14C]lactate, and [U-14C]acetate was used to study the oxidative metabolism of embryos recovered from sheep, mice and cattle. Sheep embryos showed an increasing capacity to oxidize glucose after the 4- to 8-cell stage and oxidative turnover of this substrate at the blastocyst stage was four times that at the early stages. Decarboxylation of carbon-1 of lactate followed a pattern similar to that seen for glucose oxidation, but acetate oxidation was low and did not follow the trends with development seen for the other substrates. Furthermore, estimates of incorporation of acetate into the macromolecules of sheep embryos were low compared with similar estimates for glucose and, unlike glucose, did not increase with development. Oxidation of all three substrates by mouse embryos increased with development but the rate of CO2 production from acetate was low compared with that from the other substrates. A combination of lactate or glucose with acetate had no influence on the utilization of acetate by mouse morulae/early blastocysts, nor did acetate influence utilization of the other substrates. Cattle morulae/early blastocysts also produced more CO2 from glucose and lactate than from acetate and the incorporation of carbon from acetate into the macromolecules of these embryos was less than from glucose. Overall, cattle embryos showed the greatest ability to metabolize acetate but were not as effective in using the other substrates as either sheep or mouse embryos at the same stage.