Developmentally related changes in the uptake and metabolism of glucose, glutamine and pyruvate by cattle embryos produced in vitro

Abstract

The metabolism of, and retention of radioactivity from, radiolabelled glucose, glutamine and pyruvate were measured in individual cattle embryos produced in vitro from the 2-cell to hatched blastocyst stage. Uptake was defined as the numeric sum of metabolism and retention of radiolabel. Glucose metabolism increased significantly between the 8- and 16-cell stages, but was accompanied by a much larger increase in glucose uptake. Consequently, the proportion of glucose uptake that was metabolized through the pentose-phosphate and Embden-Meyerhof pathways reached a minimum at those stages. From the compacted morula stage onward, the calculated uptake of [14C]glucose was only 25 to 33% of that calculated for [5-3H]glucose. This suggests that 66 to 75% of glucose carbon leaves the embryo, after metabolism to phosphoenolpyruvate, in some form other than CO2. Little or no glucose metabolism by the Krebs cycle could be detected at any stage. Both glutamine and pyruvate metabolism were relatively high at the 2- and 4-cell stages, declined to a minimum at the compacted morula stage and then increased with blastulation. Glutamine metabolism continued to increase with expansion and hatching of the blastocyst, but pyruvate metabolism did not. This suggest that, relative to the activity of the pathway from pyruvate to 2-oxoglutarate, the activity of the 2-oxoglutarate-to-oxaloacetate segment of the Krebs cycle is of increasing significance during expansion and hatching of the cattle blastocyst.

Effects of assisted reproductive technologies on human sex ratio at birth

“…The genes controlling glucose uptake and metabolism (glucose-6-phosphate dehydrogenase, G6PD) and anti-oxidants (hypoxanthine phosphoribosyl transferase, HPRT) are located on the X-chromosome, and thus female embryos have been reported to have higher glucose uptake and detoxification of oxygen radicals (36,37). These radicals also have a growth stimulant effect (38,39), and are not only involved in mechanisms of cellular damage. Potentially, the double dose of enzyme activity can explain the delayed development of female embryos (35) perhaps resulting in male embryos being more able to withstand stressful in vitro conditions.…”

Diphenyleneiodonium Inhibits the Cell Redox Metabolism and Induces Oxidative Stress

“…(19,20). 14 CO 2 is released when [1-14 C]glucose is metabolized either by the PPP or by the tricarboxylic acid cycle, whereas it is developed from [6-14 C]glucose only via the tricarboxylic acid cycle (21). The amount of glucose transformed into CO 2 through the PPP or tricarboxylic acid cycle was calculated as described (20,21) and expressed as nmol CO 2 /h/mg of cell proteins.…”

Can embryo metabolism be used for selecting bovine embryos before transfer?

“…The spent culture drops can also be used to evaluate amino acid uptake/release by reverse-phase HPLC [3,16,26 [23] was adapted by D. Rieger to the study of single bovine embryos [29,30]. Physiological changes in embryo metabolism might thus be associated with an increase in energy demand and/or in biosynthesis but also with modifications in embryo environment, for example in oxygen availability in the uterus before implantation where ATP formation via glycolysis may be the natural metabolic pathway [ 19].…”