Development of gluconeogenic enzymes in fetal sheep liver and kidney.
In the sheep, the system of enzymes necessary for conversion of nonhexose substrates to glucose becomes active during late fetal life. Glucose-6-phosphatase and fructose-1,6-diphosphatase, two of the four key gluconeogenic enzymes, appear in significant amounts between 100 and 120 days gestation. Phosphoenolpyruvate carboxykinase activity is comparable to mature animals as early as 45 days gestation. Two aminotransferases, necessary to allow amino acid access to the gluconeogenic pathway, likewise have substantial activity as early as 45 days gestation. Hence, the surge of glucose-6-phosphatase and fructose-1,6-diphosphatase at 100-120 days gestation makes possible the endogenous production of new glucose by fetal sheep at a time when the amount of glucose transferred from the maternal circulation is less than the total aerobic substrate utilized by the fetus. Both renal cortex and liver have similar developmental patterns for the gluconeogenic enzymes, although renal cortex generally shows greater activity than liver. This observation holds true for tissue from both fetal and mature animals.
Program in Pediatrics, University of Texas Health Science Center at Houston, Medical School, 6400 West Cullen Street, Houston, Texas 77025, USA.
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Stevenson
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Morriss
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Adcock
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Howell
D000818:Animals; D000831:Animals, Newborn; D001219:Aspartate Aminotransferases / Q000378:metabolism; D018826:CD13 Antigens / Q000378:metabolism; D004798:Enzymes / Q000378:metabolism*; D005260:Female; D006597:Fructose-Bisphosphatase / Q000378:metabolism; D005865:Gestational Age; D005952:Glucose-6-Phosphatase / Q000378:metabolism; D007668:Kidney / Q000196:embryology* / Q000201:enzymology*; D008099:Liver / Q000196:embryology* / Q000201:enzymology*; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism; D012756:Sheep / Q000196:embryology
D004798:Enzymes; D001219:Aspartate Aminotransferases; D006597:Fructose-Bisphosphatase; D005952:Glucose-6-Phosphatase; D018826:CD13 Antigens; D019764:Phosphoenolpyruvate Carboxykinase (ATP)