The accumulation of substrate carbon by mouse embryos was measured following incubation in U-14C-glucose. Following a 30-min incubation period 273 × 10-14 and 301×10-14g atoms of substrate carbon per embryo were found in 2- and 8-cell embryos respectively. By comparison, the figures for unfertilized and fertilized ova were 14 × 10 -14 and 45 × 10-14 g atoms of substrate carbon.
The intracellular concentration of substrate carbon was timedependent in both 2- and 8-cell embryos. After an 80-min incubation, substrate carbon in the 8-cell embryo was almost double that in the 2-cell embryo. Accumulation did not occur during incubations at 5° C and there was competition between glucose and galactose for uptake. The results are discussed in relation to the energy requirements of the developing zygote.
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