Hexokinase Is a Key Enzyme of Glucose Metabolism Expressed during Preimplantation Mouse Development

Abstract

Glucose incorporation and utilization in mouse embryos increases during preimplantation development, which may depend at least in part on the hexokinase activity in the embryos. Microdetermination methods including NADP cycling were used to quantitatively examine the enzymatic activity of hexokinase. Hexokinase activity in 1-cell embryos was low (0.035 ± 0.010 pmol of NADPH formed/embryo/min), but progressively increased during preimplantation development. Although there is a significant delay, this increase is also observed when 2-cell embryos are developed in vitro. This increase in hexokinase activity was inhibited by the administration of actinomycin-D in the medium. A reverse transcription-polymerase chain reaction was used to study the expression of hexokinase mRNA in preimplantation mouse embryos. Messenger RNA was obtained from 100 of 2-cell embryos and blastocysts using the Micro-Fast Track mRNA isolation kit. Hexokinase mRNA is detectable after the 2-cell embryo stage. The levels of mRNA increased during embryonic development. These results suggest that hexokinase may be a key enzyme synthesized as the expression of zygotic genome in preimplantation embryos, and help in assessing the quality of embryos developed in vitro.