The basics of phosphate metabolism.

Phosphorus is an essential mineral that is under the form or inorganic phosphate (Pi) required for building cell membranes, DNA and RNA molecules, for energy metabolism, signal transduction or pH buffering. In bone, Pi is essential for bone stability under the form of apatite. Intestinal absorption of dietary Pi depends on its bioavailability and has two distinct modes of active transcellular and passive paracellular absorption. Active transport is transporter mediated and partly regulated, passive absorption depends mostly on bioavailability. Renal excretion is controlling systemic Pi levels, depends on transporters in the proximal tubule and is highly regulated. Deposition and release of Pi into and from soft tissues and bone has to be also tightly controlled. The endocrine network coordinating intestinal absorption, renal excretion and bone turnover integrates dietary intake, metabolic requirements with renal excretion and is critical for bone stability and cardiovascular health during states of hypophosphatemia or hyperphosphatemia as evident from inborn or acquired diseases. This review provides an integrated overview over the biology of phosphate and Pi in the mammalian organism.