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Hepatic protein synthesis in suckling rats: effects of stage of development and fasting
D G Burrin1, T A Davis, M L Fiorotto
1USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030.
Insights
Hepatic protein synthesis in suckling rats shows a biphasic developmental pattern, increasing during neonatal and weaning periods. Fasting impacts protein synthesis more significantly in neonatal rats compared to later stages.
Area of Science:
- Biochemistry
- Developmental Biology
- Physiology
Background:
- Hepatic protein synthesis is crucial for liver development and function.
- Understanding developmental changes and the impact of nutritional status is vital for pediatric health.
Purpose of the Study:
- To investigate developmental changes in hepatic protein synthesis in suckling rats.
- To examine the effect of fasting on hepatic protein turnover during postnatal development.
Main Methods:
- In vivo fractional protein synthesis rates (KS) measured using L-[4-3H]phenylalanine flooding dose.
- Studies conducted on suckling rats from postpartum day 1 to 28.
- Fasting protocols included 10 or 18 hours at various developmental stages.
Main Results:
- Hepatic protein synthesis and translational efficiency exhibited a biphasic pattern, peaking at postnatal days 10 and 28.
- The most significant increase in synthesis and efficiency occurred during the weaning period (days 16-28).
- Fasting reduced synthesis and efficiency, with the greatest relative decline observed at postnatal day 10.
Conclusions:
- Postnatal hepatic protein synthesis in rats follows a biphasic developmental trajectory, with increases during neonatal and weaning phases.
- Fasting exerts a more pronounced relative effect on hepatic protein synthesis during the neonatal period compared to later suckling and weaning stages.
Abstract:
We studied the developmental changes in hepatic protein synthesis in suckling rats between postpartum d 1 and 28 and investigated the effect of fasting for 10 or 18 h on hepatic protein turnover at postpartum d 5, 10, 16, and 28. Fractional protein synthesis rates (KS, %/d) were measured in vivo using a flooding dose of L-[4-3H]phenylalanine. Although hepatic KS and translation efficiency (protein synthesis/unit RNA) were significantly higher at postpartum d 28 than d 1, the pattern of change was biphasic: KS and translational efficiency were higher at d 10 and 28 than at d 5 and 16. The largest increase in KS and translational efficiency occurred during the period normally associated with weaning (between postpartum d 16 and 28). At all stages of development, the KS and translational efficiency in fasted rats were significantly lower than those in control (fed) rats, although the relative decline in both measurements was largest at postpartum d 10. The absolute rates of hepatic protein synthesis declined to similar levels on d 5, 10, and 16 after 10 h of fasting and changed little after 18 h of fasting; this level was significantly higher at postpartum d 28. Our results suggest that postnatal development in suckling rats was marked by a biphasic pattern in the rates of hepatic protein synthesis, which increased during the neonatal and weaning periods. The relative changes in the synthesis and loss of hepatic protein in response to fasting were greater during the neonatal than during the late suckling and weaning periods.