Glucose metabolism in separated embryos and investing membranes during organogenesis in the rat.
Glucose metabolism provides an essential energy source in the mammalian embryo. We used the rat embryo culture system to investigate the activity of several critical pathways for glucose metabolism during early organogenesis, before (day 10 of gestation) and during (day 11) the establishment of the chorioallantoic circulation and closure of the neural tube. We studied glucose metabolism in the intact conceptus, the separated embryo, and its investing membranes, including the visceral yolk sac, allantois, and amnion. Short-term incubations were performed for 4 hours in culture media containing U-14C-, 14C-1-, or 14C-6-labeled D-glucose on day 10 and day 11 of gestation, and the rates of glucose utilization by glycolysis and oxidative metabolism, including the pentose phosphate pathway (PPP), were measured. Glycolytic metabolism, estimated by the accumulation of lactate, was high on day 10 in the intact conceptus, embryo, and membranes (92 +/- 6, 63 +/- 5, and 99 +/- 8 nmol/micrograms protein/4 h, respectively) and decreased by two thirds by day 11 in each tissue. Of note, the rate of glycolysis was greater in membranes than in the embryo on both days (P < .01). On the other hand, oxidative metabolism, reflected in the production of 14CO2, was relatively low on day 10 (0.78 +/- 0.04, 0.73 +/- 0.05, and 0.6 +/- 0.06 nmol/micrograms protein/4 h for intact conceptus, embryo, and membranes, respectively) and increased significantly in each tissue by day 11 (P < .01 for each).
Akazawa
S
S
First Department of Internal Medicine, Nagasaki University School of Medicine, Japan.
Unterman
T
T
Metzger
B E
BE
D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002952:Citric Acid Cycle; D004247:DNA / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism*; D005314:Embryonic and Fetal Development; D005321:Extraembryonic Membranes / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D010084:Oxidation-Reduction; D010427:Pentose Phosphate Pathway; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D007773:Lactates; D011506:Proteins; D002245:Carbon Dioxide; D019344:Lactic Acid; D004247:DNA; D005947:Glucose