[Molecular physiology and pathophysiology of renal phosphate excretion]

The kidney is a key organ in phosphate homeostasis. Phosphate excretion is largely determined by free glomerular filtration and by regulated reabsorption in the proximal tubule. The cellular/molecular mechanisms involved in phosphate reabsorption have been elucidated in great detail over the past few years. A brush border membrane protein with most probably 8 membrane-spanning regions represents the rate-limiting and physiologically/pathophysiologically modified transport mechanism. Altered phosphate reabsorption correlates with an altered brush border membrane transporter protein content, altered either by new synthesis/membrane insertion or by membrane retrieval/degradation. Current knowledge on the molecular/cellular level is a prerequisite for an understanding of kidney based alterations in phosphate homoeostasis.