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Intestinal absorption of bile salts: immature development in the neonate
Insights
The ileal active transport of bile salts like sodium taurocholate is underdeveloped in newborns. This immaturity may explain bile salt loss, leading to diarrhea in infants.
Area of Science:
- Gastroenterology
- Neonatal Physiology
- Bile Salt Metabolism
Background:
- Bile salt absorption is crucial for digestion and nutrient absorption.
- The development of intestinal transport mechanisms varies across age groups.
- Enterohepatic circulation of bile salts is essential for efficient bile salt reabsorption.
Purpose of the Study:
- To investigate the developmental changes in intestinal sodium taurocholate absorption.
- To determine the age at which active ileal bile salt transport matures.
- To explore the implications of immature bile salt absorption in newborns.
Main Methods:
- In vitro study using everted rings of jejunum and ileum from fetuses, neonates, infants, children, and adults.
- Measurement of 3H-taurocholate mucosal accumulation against a concentration gradient.
- Analysis of taurocholate uptake at varying concentrations (0.003, 0.03, and 0.3 mM) and assessment of saturation kinetics.
Main Results:
- Active sodium taurocholate transport was demonstrated in the ileum of infants (older than 8 months), children, and adults.
- Fetal and neonatal ileal tissues showed no significant active taurocholate accumulation.
- Jejunal and ileal uptake did not differ significantly in perinatal tissues, indicating a lack of specific ileal transport.
- Saturation of taurocholate uptake was observed in older individuals, suggesting a carrier-mediated process.
Conclusions:
- The ileal active transport mechanism for sodium taurocholate is immature at birth.
- Bile salt absorption in newborns is likely limited to passive diffusion.
- Impaired bile salt absorption in neonates may contribute to steatorrhea and diarrhea.
- Understanding these developmental changes is vital for managing neonatal gastrointestinal issues.
Abstract:
The intestinal absorption of sodium taurocholate was studied in fetuses, neonates, infants, children, and adults. Absorption rates were measured in vitro in everted rings of jejunum and ileum. Mucosal accumulation of 3H-taurocholate against a concentration gradient was consistently demonstrated in rings of ileum from adults, children, and infants older than 8 months, whereas fetal and neonatal ileal mucosal concentrations were not significantly above those in the incubation medium after exposure of the mucosa to 0.003, 0.03, and 0.3 mM taurocholate. There were no significant differences in mucosal uptake of taurocholate by perinatal jejunal and ileal rings. Incubations of mucosa from older infants, children, and adults in 0.3 mM taurocholate exhibited saturation phenomena. It is concluded that the ileal mechanism for active transport of taurocholate is undeveloped in the fetus and newborn infant. It is probable that the enterohepatic circulation of bile salt during the perinatal period is limited to that fraction of bile salt absorbed passively. The results suggest that losses of bile salt from the immature intestine may contribute to the steatorrhea and so-called diarrhea of newborn infants.