Potassium homeostasis: ontogenic aspects.

Potassium is the most abundant intracellular cation and plays an important role in a variety of cell functions. Potassium regulation and homeostasis during infancy are, owing to growth and development, different from in later life: infants need to retain more K+ than adults, to avoid growth retardation. Since the K+ requirements are different in infants and in adults, the mechanisms regulating K+ homeostasis also need to be different. This paper includes a review of the literature concerning the regulation of internal and external K+ balances during ontogeny. We examined the role of gastrointestinal tract, kidney and some tissue stores in K+ excretion and distribution during development. We conclude that positive K+ balance in infancy is characterized by higher K+ absorption in gut, lower K+ secretion/excretion in kidney and immaturity of the mechanisms regulating intra/extracellular K+ distribution. Several factors contribute to maintain the positive K+ balance. They include higher expression of absorptive transporters in colon and probably in kidney, lower expression of secretive transporters in colon and kidney, lower renal K+ excretion following K+ loading, immaturity of hepato-renal K+ reflex mechanism, immaturity of tissue K+ binding/releasing capacity and immaturity of the neuro-hormonal control of K+ transport in several organs.