Net sodium and water movements in the newborn rabbit collecting tubule: lack of modifications by indomethacin.

In contrast to adult tubules, a bath-to-lumen sodium gradient was followed by net sodium entry in the lumen of in vitro isolated perfused newborn (3-5 days) rabbit collecting tubules. In addition, transepithelial voltage and electrical resistance were lower in newborn tubules. The sodium flux into the lumen was unaffected by indomethacin. These observations suggest that the newborn collecting tubule may be unable to maintain an adequate sodium gradient for the optimal function of the urinary concentrating mechanism, and that endogenous prostaglandins are not involved in this defect.