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Brain growth during ethanol-induced hypoplasia
1Department of Biochemistry, East Carolina University, Greenville, NC 27834.
Insights
Ethanol exposure in ovo inhibits fetal brain growth by reducing DNA and protein synthesis, increasing prostaglandin E, and decreasing cyclic AMP. These effects correlate with blood alcohol levels but are reversible by day 10.
Area of Science:
- Neuroscience
- Developmental Biology
- Toxicology
Background:
- In utero ethanol exposure can lead to central nervous system (CNS) developmental issues and mental retardation.
- Chick embryo studies show ethanol inhibits early growth, but weight is often regained by hatching.
- Biochemical changes during varying growth rates in alcohol-exposed embryos require investigation.
Purpose of the Study:
- To investigate the biochemical alterations linked to growth changes in ethanol-exposed chick embryos.
- To understand the relationship between ethanol dosage, blood alcohol content, and CNS development.
- To explore the role of prostaglandin E (PGE) and cyclic AMP in ethanol-induced developmental effects.
Main Methods:
- Administered a single dose of ethanol (1.0 g/kg) to chick embryos at day 0 of incubation.
- Measured rates of DNA and protein synthesis via radioactive thymidine and leucine incorporation.
- Assessed blood alcohol content, brain prostaglandin E (PGE) levels, and brain cyclic AMP content.
- Correlated biochemical data with individual brain weight and developmental stage.
Main Results:
- Ethanol significantly inhibited DNA and protein synthesis rates between days 5 and 8 of development.
- Growth inhibition correlated with blood alcohol content and increased brain PGE levels.
- A significant inverse correlation was observed between brain cyclic AMP and brain weight.
- By day 10, synthesis rates normalized, correlating with ethanol clearance and PGE restoration.
Conclusions:
- Early ethanol exposure disrupts fetal brain growth through biochemical pathways involving DNA/protein synthesis and prostaglandin E.
- The observed effects are dose-dependent and linked to blood alcohol concentration.
- Reversibility of biochemical changes by day 10 suggests a potential for recovery if ethanol is cleared.
- Findings highlight the critical window of vulnerability during early embryonic development to ethanol teratogens.
Abstract:
The inhibition of fetal brain growth resulting from in utero ethanol exposure may impair central nervous system (CNS) development and thereby result in mental retardation. Studies of ethanol-induced brain hypoplasia using chick embryos have shown that the early development of the chick is significantly growth inhibited by a single dose of ethanol (1.0 g/kg) given at the start of incubation (day 0). However, this level of ethanol exposure has been reported to have no effect on chick weight measured at hatching, suggesting that the weights of ethanol-treated chicks were regained during their development. The present experiments were undertaken to determine the biochemical changes associated with the varying growth rates believed to occur in the alcohol-treated embryos. The results indicated that between days 5 and 8 of development, the rates of DNA and protein synthesis (measured as radioactive thymidine and leucine incorporation, respectively) were inhibited by ethanol. The growth inhibition was highly correlated with blood alcohol content and there were associated increases in brain prostaglandin E (PGE) levels relative to vehicle-treated embryos. Further, there was a significant, inverse correlation between brain cyclic AMP content and individual brain weight. By day 10, the ethanol-treated embryos remained smaller than controls but their rates of DNA and protein synthesis were comparable to those of control animals. The normal rates of synthesis observed on day 10 appeared to correlate with clearance of the ethanol dose and with restoration of normal brain levels of PGE relative to 10-day vehicle-dosed embryos.