Abstract:
Transporters move molecules across cell membranes and are distributed in various tissues. Very little is known about their
ontogenic expression, especially in intestine and brain. The purpose of the present study was to determine whether
transporters that are predominantly expressed in duodenum and brain are expressed similarly in newborn and adult mice. In duodenum, AbcG5 and AbcG8, which are important in decreasing the absorption of plant steroids, have similar patterns of
expression, reaching their maximal expressions at 15- to 22-days of age. Organic solute transporters, Ostα and Ostβ, which function in bile acid absorption, and multidrug resistance-associated protein Mrp2, which contributes to the intestinal excretion of many xenobiotics, are higher at birth than in the adult duodenum. In contrast, a dipeptide-uptake transporter, Pept1, does not reach adult levels until 30-days of age. Concentrative nucleotide transporters Cnt1, 2, and 3 do not vary with age. In brain, the organic anion transporting polypeptide Oatp1a4 exhibits a gradual increase with age, reaching adult values by 30-days of age, whereas Oatp1c1 reaches adult levels by 5-days of age. Three other highly expressed transporters in brain, namely Mrp4, Mrp5, and Ent2, do not show variation with age. In conclusion, transporters in both the duodenum and brain depict different ontogenic expression patterns. These age-dependent expression patterns might be responsible for some of the differences in pharmacological and toxicological effects of xenobiotics between newborns and adults.
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