Influence of Environmental Factors on the Metabolism of Glucose by Preimplantation Mouse Embryos in vitro

Abstract

The metabolism of glucose by late pre implantation mouse embryos was studied in a variety of media whose composition had been changed to reflect the environmental conditions in the uterus more closely than do standard culture media. The effects of combinations of energy substrates, the presence or absence of amino acids and the level of potassium in the medium were investigated.The use of energy substrates for in vitro culture at levels present in the uterine environment resulted in rates of synthesis and degradation of glycogen pools similar to those obtained using standard in vitro culture conditions but elevated incorporation into non-glycogen macromolecules. Amino acids influenced the metabolism of glucose by limiting the entry of glucose carbon into the non-glycogen macromolecular pool and directing more glucose into the synthesis of acid-soluble glycogen.Increasing the K + concentration to 60 mM in the culture medium caused a small but significant increase in the number of eight-cell embryos degenerating during culture for 24 h but the metabolism of glucose was unaffected over this time. At the time of morula transformation to the blastocyst this level of potassium ions suppressed glycogen synthesis by 50% over 5 h but did not affect its turnover during chase culture.It is concluded that factors other than those studied here contribute to the maintenance of the low glycogen levels found in uterine embryos. IntrodnctionEarlier work (Ozias and Stern 1973;Ozias and Weitlauf 1971;Snyder et al. 1971;Edirisinghe et al. 1984aEdirisinghe et al. , 1984b indicates that the uterine environment influences the metabolism of late preimplantation mouse embryos and in particular the utilization of glycogen stores. This environment is more complex than, and differs in the range and concentration of components from, the standard chemically defined media normally used for in vitro culture (Hamner 1971;Wales 1973;Beier 1974; Edirisinghe and Wales 1985). Changes in the environment may well be important in modifying the metabolism of glucose by embryos and be responsible for the differences in the turnover of glycogen in vivo as compared to its utilization in vitro.The possible control of glycogen metabolism by the level of exogenous energy substrate has been studied using different concentrations of the major energy substrates, glucose, lactate and pyruvate (Pike and Wales 1982). It is clear from this study that embryos, especially at the late preimplantation stages, have the ability to synthesize large amounts of glycogen and that the presence of the alternative energy substrates, lactate and pyruvate during culture influences the synthesis of glycogen, particularly when the medium contains a low concentration of glucose. Recently, the levels of lactate, pyruvate and glucose in the uterine fluid of mice have been measured and found 0004-9417/85/040411 $02.00

Implications of Glucose Transporter Protein Type 1 (GLUT1)-Haplodeficiency in Embryonic Stem Cells for Their Survival in Response to Hypoxic Stress

“…One important functional difference between them is that GLUT3 may transport glucose at a higher rate than GLUT1, 58,59 potentially seven times faster, and therefore may be better suited to transport maternal glucose into the preimplantation embryo that encounters a low-glucose (1 mmol/L) environment. 56,60 GLUT1 is then proposed to transport glucose into the embryonic cells for metabolism. 56 Our investigations of facilitative glucose transporters in ES cells found that both GLUT1 and GLUT3 were expressed, whereas GLUTs 2, 4, and 9 were not.…”

Glucose transporter GLUT3: Ontogeny, targeting, and role in the mouse blastocyst

“…The GLUT most likely to be expressed in an apical location in TE and therefore responsible for the uptake of maternal glucose was GLUT3. Primarily found in neurons (13)(14)(15), this isoform has an apical distribution in other polarized epithelial cells (11,12) and its extremely low K m [10.6 Ϯ 1.3 mM for 3-OMG (10)], matching that of blastocysts would ensure efficient glucose uptake by the embryo at the low glucose levels prevailing in the uterus (16).…”

In Vitro Fertilization

“…Although the mouse blastocyst is capable of metabolizing exogenous steroid hormones (225), there is limited data on the direct action of hormones on the early embryo (226)(227)(228)(229). Certainly, estradiol appears to have a direct negative impact on mouse embryo development (230,231).…”