ABSTRACT
The renal handling of phosphorus, in the form of the phosphate anion (Pi), is of predominant importance in the maintenance of Pi body pool size.1 In contrast to calcium, whose absorption is highly regulated, the phosphate intestinal anion is largely unregulated and net Pi absorption is directly related to its dietary intake.2 Hence, Pi homeostasis is dependent on a variety of mechanisms that influence its urinary excretion. Because Pi is a major determinant of oxidative phosphorylation, membrane protein phosphorylation, energy transfer, and bone mineral status, the renal processes that result in Pi reabsorption and excretion are complex. This chapter focuses on the process of renal Pi handling, beginning with the overall characteristics of PI reabsorption, noting the tubule segments where Pi reabsorption occurs, the membrane and cellular processes which determine Pi reabsorption, and the regulatory factors that influence Pi excretion.
