Postnatal development and inducibility of renal tubular transport processes in rats.

The reason for the immaturity and for the time course of postnatal development of renal tubular transport of organic anions was studied, measuring age differences in renal tubular transport of p-aminohippurate (PAH) under various experimental conditions. In principle, PAH transport can be stimulated by repeated administration of weak organic anions, which were eliminated by the carrier system for weak organic anions. However, there is nearly no effect in neonatal rats. Pretreatment with thyroid hormones can enhance the low tubular transport capacity of young rats, too. Pretreatment with dexamethasone is preferentially effective in 5- to 15-day-old rats. The data indicate the involvement of hormonal regulation in postnatal development of renal tubular transport of PAH.