Development of tubular function.

This article has reviewed the maturation of major renal tubular transport systems. The tubular reabsorption of certain amino acids and the secretion of organic acids, hydrogen ions, and potassium increases as a function of postnatal age, being relatively immature at birth, especially in the preterm infant. In contrast, the ability for phosphate reabsorption is enhanced during the immature state as the developing animal attempts to adapt to its environment. In the case of glucose, the transport system is relatively mature in the term infant and less so in the infant of less than 34 weeks' gestation. One should consider these developmental changes in the renal tubular transport of amino acids, potassium, phosphate, and organic acids in the nutritional assessment and pharmacologic treatment of preterm as well as term infants.