Parathyroid hormone (PTH) effects on renal inorganic phosphate reabsorption. Renal reabsorption of phosphate occurs through apical sodium (Na+)–
inorganic phosphate (Pi) cotransport. Three different Na+/Pi cotransporters have been identified: types I, II, and III. Type I and type II cotransporters are
located in the apical membrane. Type II cotransporters are expressed in the renal proximal tubule (type IIa) and in the small intestine (type IIb). Type IIa
cotransporters are the major target for PTH regulation and contribute to most (up to 70%) of proximal tubular Pi reabsorption. PTH acutely stimulates
internalization of the type IIa cotransporters, directing them to the lysosomes for destruction. Type III cotransporters are most likely located at the
basolateral membrane and play a general “housekeeping”
role in ensuring basolateral Pi influx if apical Pi entry is insufficient to satisfy cellular
Source: Chapter 5. Parathyroid Gland and Ca2+ and PO4- Regulation, Endocrine Physiology, 4e
requirements. Basolateral exit, which is necessary to complete transcellular
Pi reabsorption, is not well defined. Several Pi transport pathways have been
Citation:Na-Pi
Molina
PE. Endocrine
at: http://mhmedical.com/
Accessed: July 31, 2017
suggested including
cotransport,
anionPhysiology,
exchange, 4e;
and2013
evenAvailable
an “unspecific”
Pi channel.
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