Effects of dietary Pi on the renal Na+-dependent Pi transporter NaPi-2 in thyroparathyroidectomized rats

Biochem J. 1998 Jul 1;333 ( Pt 1)(Pt 1):175-81. doi: 10.1042/bj3330175.

Abstract

Dietary Pi and parathyroid hormone (PTH) are two most important physiological and pathophysiological regulators of Pi re-absorption in the renal proximal tubule. Effects of dietary Pi on Na+/Pi co-transporter NaPi-2 were investigated in thyroparathyroidectomized (TPTX) rats. NaPi-2 protein and mRNA in the kidney cortex of TPTX rats were increased approximately 3.8- and 2.4-fold in amount respectively compared with those in the sham-operated animals. Administration of PTH to the TPTX rats resulted in a decrease in the amount of NaPi-2 protein, but not in the abundance of NaPi-2 mRNA. Deprivation of dietary Pi in the TPTX rats did not affect the amount of NaPi-2 mRNA and protein. In the Pi-deprived TPTX rats, feeding of a high-Pi diet resulted in marked decreases in Pi transport activity and the amount of NaPi-2 protein in the superficial nephrons. Immunohistochemical analysis demonstrated that administration of PTH to TPTX rats resulted in a decrease in NaPi-2 immunoreactivity from both superficial and juxtamedullary nephrons within 4 h. Switching TPTX animals from a low-Pi diet to the high-Pi diet decreased NaPi-2 immunoreactivity from superficial nephrons, but not from juxtamedullary nephrons, within 4 h. These results suggest that dietary Pi could regulate the amount of NaPi-2 protein in the superficial nephrons in a PTH-independent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Carrier Proteins / biosynthesis
  • Carrier Proteins / metabolism*
  • Endocytosis / physiology
  • Immunoblotting
  • Kidney / drug effects*
  • Kidney / metabolism
  • Kidney / ultrastructure
  • Kidney Cortex / drug effects
  • Kidney Cortex / metabolism
  • Kidney Cortex / ultrastructure
  • Male
  • Microvilli / drug effects
  • Microvilli / metabolism
  • Nephrons / drug effects
  • Nephrons / metabolism
  • Parathyroid Hormone / metabolism
  • Parathyroid Hormone / pharmacology
  • Parathyroidectomy
  • Phosphates / administration & dosage
  • Phosphates / pharmacology*
  • Phosphorus, Dietary / administration & dosage
  • Phosphorus, Dietary / pharmacology*
  • RNA, Messenger / biosynthesis
  • Rats
  • Rats, Sprague-Dawley
  • Sodium-Phosphate Cotransporter Proteins
  • Symporters*
  • Thyroidectomy

Substances

  • Carrier Proteins
  • Parathyroid Hormone
  • Phosphates
  • Phosphorus, Dietary
  • RNA, Messenger
  • Sodium-Phosphate Cotransporter Proteins
  • Symporters