Effects of antenatal glucocorticoids on cerebral protein synthesis in the preterm ovine fetus
| Autor: | Peter W. Nathanielsz, Turhan Coksaygan, Norman B. Smith, Bryan S. Richardson, Matthias Schwab, Jeremy D. McCallum, James N. MacLachlan |
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| Rok vydání: | 2008 |
| Předmět: |
medicine.medical_specialty
Litter Size medicine.medical_treatment Coefficient of variation Gestational Age Betamethasone Injections Intramuscular Random Allocation Pregnancy Reference Values Internal medicine medicine Animals Glucocorticoids Saline Sheep Domestic Fetus business.industry Brain Membrane Proteins Obstetrics and Gynecology Gestational age medicine.disease Disease Models Animal Endocrinology Maternal Exposure Protein Biosynthesis Gestation Female business Blood Flow Velocity Glucocorticoid medicine.drug |
| Zdroj: | American Journal of Obstetrics and Gynecology. 198:103.e1-103.e6 |
| ISSN: | 0002-9378 |
| DOI: | 10.1016/j.ajog.2007.05.008 |
| Popis: | Objective Although antenatal glucocorticoids have well-known benefits for infants who are born preterm by the enhancement of pulmonary maturation, adverse effects on brain growth and development have been reported in several animal-based studies. We have used the chronically catheterized ovine fetus to determine the effects of synthetic glucocorticoids that are administered at doses used clinically on cerebral protein synthesis during early brain development using [ 13 C]-leucine tracer method. Study Design Chronically instrumented pregnant sheep at 0.85 gestation received 2 intramuscular injections of betamethasone at 170 μg/kg maternal weight or saline 24 hours apart together with a continuous infusion of L-[1- 13 C]-leucine to the fetus on the second day of experimentation. Measurements were obtained for fetal plasma leucine enrichment at steady-state and brain tissue intracellular free and protein-bound leucine enrichment at necropsy, followed by the determination of cerebral protein fractional synthetic rates (FSRs). A coefficient of variation was determined for plasma and tissue enrichment measurements to assess the inherent methodologic variance with the use of [ 13 C]-leucine tracer technology. Results The cerebral protein FSR averaged approximately 112% per day and approximately 35% per day when the intracellular free and plasma enrichment values were used for the precursor pool measurements, respectively, providing for maximal and minimal FSR values. There were no differences between cortical and cerebellar tissues nor between the saline control and the betamethasone animal groups. The coefficient of variation for the plasma-enrichment values averaged approximately 2%; the coefficient of variation for the tissue enrichment values averaged approximately 10%, with an inverse relationship between the [ 13 C]-leucine enrichment values and the coefficient of variation values. Conclusion Although cerebral FSR values for the preterm ovine fetus are high and indicate high rates of protein synthesis and degradation, we found no evidence that these are altered by betamethasone as used clinically and thereby do not account for the reported structural alterations in the brain after a single-course of antenatal glucocorticoids. |
| Databáze: | OpenAIRE |
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