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Glucose metabolism in the trophectoderm and inner cell mass of the rabbit embryo
1Department of Physiology and Biophysics, University of Alabama, Birmingham 35294.
Insights
Rabbit blastocysts show low glucose metabolism, with no significant difference between the trophectoderm and inner cell mass (ICM) in Day-7 embryos. Glucose is not the primary metabolic fuel for early rabbit embryonic development.
Area of Science:
- Developmental biology
- Embryology
- Metabolic research
Background:
- Understanding nutrient utilization is crucial for early embryonic development.
- Glucose metabolism pathways in preimplantation embryos are not fully elucidated.
- Rabbit blastocysts represent a model for studying early embryonic nutrient uptake.
Purpose of the Study:
- To investigate glucose metabolism in intact and separated rabbit blastocyst compartments.
- To determine the role of glucose as a metabolic substrate in early rabbit embryos.
- To compare glucose utilization between the trophectoderm and inner cell mass (ICM).
Main Methods:
- Studied glucose metabolism in Day-6 and Day-7 post coitum (p.c.) rabbit blastocysts.
- Utilized separated trophectoderm and ICM from Day-7 p.c. embryos.
- Measured CO2 production from glucose and lactate production.
Main Results:
- Day-6 blastocysts metabolized glucose to CO2 at 25.5 nmol.cm-2.h-1; lactate production was largely glucose-independent.
- Glucose metabolism to CO2 significantly decreased in intact Day-7 blastocysts (7.76 nmol.cm-2.h-1).
- Glucose metabolism rates were similar in separated Day-7 trophectoderm and ICM.
Conclusions:
- Rabbit blastocysts exhibit limited dependence on glucose for metabolism.
- The inner cell mass (ICM) does not show higher glucose utilization than the trophectoderm in Day-7 embryos.
- Glucose is likely not a primary metabolic fuel for the rabbit blastocyst during these early stages.
Abstract:
The metabolism of glucose in the intact Day-6 and -7 post coitum (p.c.) rabbit blastocyst and in the separated trophectoderm and inner cell mass (ICM) of the Day-7 p.c. embryo was investigated. At Day-6 p.c., glucose traversed the trophectoderm with a half-time of 39 +/- 9.3 min, and was metabolized to CO2 at a rate of 25.5 +/- 1.6 nmol.cm-2.h-1. Neither the Na+ ionophore, amphotericin B, nor cyclic AMP had an effect on glucose metabolism to CO2. Lactate production by the Day-6 blastocyst was largely independent of glucose. At Day-7 p.c. in the intact embryo, CO2 production from glucose significantly decreased to 7.76 +/- 2.8 nmol.cm-2.h-1. Per unit surface area, the metabolism of glucose to CO2 was similar in the separated Day-7 p.c. trophectoderm and ICM. We conclude that the rabbit blastocyst is not highly dependent on glucose, and that the ICM does not utilize glucose as a metabolite to a greater extent than does the trophectoderm, at least in the Day-7 p.c. embryo.