The increase in fetal hemoglobin synthesis in the fetal lamb during hyperglycemic hypoxemia.
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Abstract
To determine whether fetal hypoxemia induced by hyperglycemia has any effect on the proportions of fetal and adult hemoglobin synthesized during fetal development, hemoglobin synthesis was determined after a period of hyperglycemic hypoxemia in the fetal lamb. These experiments were carried out at a time in gestation during the switch from fetal to adult hemoglobin. Twelve catheterized fetal sheep were included in this study. Seven were made hyperglycemic by glucose infusions during 5 days (group I) and five were control animals (group II) that received saline solution infusions (0.45 gm/dl). In group I, glycemia increased from 14.7 +/- 5.0 to 54.6 +/- 16.4 mg/dl (p less than 0.001), whereas oxygen content decreased from 8.5 +/- 1.7 to 6.4 +/- 2.2 ml/dl (p less than 0.01). Red blood cells obtained before and after 5 days of glucose or saline solution infusions were incubated in an amino acid mixture containing 14C-leucine. The hemoglobins were then subjected to polypeptide chain elution with carboxymethyl cellulose chromatography. The amount of fetal hemoglobin synthesized was determined by the ratio of radioactive gamma-chain to total of radioactive non-alpha-chains. The data demonstrated that the hyperglycemic fetus synthesizes more fetal hemoglobin than expected for the period of fetal development (78.0% +/- 10.9% versus 59.8% +/- 11.3%, p less than 0.02).