OXIDATIVE UTILIZATION OF GLUCOSE, ACETATE AND LACTATE BY EARLY PREIMPLANTATION SHEEP, MOUSE AND CATTLE EMBRYOS

The production of radiolabelled CO2 from [U-C-14]glucose, [1-C-14]lact ate, and [U-C-14]acetate was used to study the oxidative metabolism of embryos recovered from sheep, mice and cattle. Sheep embryos showed a n increasing capacity to oxidize glucose after the 4- to 8-cell stage and oxidative turnover of this substrate at the blastocyst stage was f our times that at the early stages. Decarboxylation of carbon-1 of lac tate followed a pattern similar to that seen for glucose oxidation, bu t acetate oxidation was tow and did not follow the trends with develop ment seen for the other substrates. Furthermore, estimates of incorpor ation of acetate into the macromolecules of sheep embryos were low com pared 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 combi nation of lactate or glucose with acetate had no influence on the util ization of acetate by mouse morulae/early blastocysts, nor did acetate influence utilization of the other substrates. Cattle morulae/early b lastocysts also produced more CO2 from glucose and lactate than from a cetate and the incorporation of carbon from acetate into the macromole cules of these embryos was less than from glucose. Overall, cattle emb ryos showed the greatest ability to metabolize acetate but were not as effective in using the other substrates as either sheep or mouse embr yos at the same stage.