Further Studies on the Accumulation of Energy Substrates by Two-cell Mouse Embryos

Abstract

The accumulation of substrate carbon by two-cell mouse embryos after incubation for 30 min in isotopically labelled substrates was compared by two different methods. The embryos were centrifuged either through an isotonic sucrose solution to free them from radioactive medium before counting or in radioactive medium in a capillary tube when substrate uptake was calculated from the relative counts in packed embryos and incubation medium.Measurements of the accumulation of substrate carbon from [1_ 14 C]pyruvate gave the same values by both methods, but the accumulation of C-1 of lactate was much greater after centrifuging the embryos in a capillary tube. Fractionation of the intracellular isotope accumulated from lactate showed that the increased radioactivity accumulated was associated with the parent substrate. A similar difference was found in the accumulation of C-1 of acetate with the two methods of recovery, indicating that both substrates diffuse freely between the medium and embryo. Incorporation of acetate into two-and eight-cell mouse embryos was similar. No intracellular substrate carbon was accumulated from [1,[5][6][7][8][9][10][11][12][13][14] C]citrate by two-cell mouse embryos during 30 min incubation.