Distribution of the sodium/phosphate transporter during postnatal ontogeny of the rat kidney

J Am Soc Nephrol. 1999 Jul;10(7):1407-15. doi: 10.1681/ASN.V1071407.

Abstract

Renal phosphate reabsorption via the type II sodium/ phosphate cotransporter (NaPi-2) in the brush border membrane (BBM) of proximal tubules underlies alterations during aging. The ontogeny of NaPi-2 in kidneys from newborn to 6-wk-old rats was investigated. NaPi-2 protein distribution in the kidneys of neonatal, 13-d-old, 22-d-old, and 6-wk-old rats was immunohistochemically analyzed, and NaPi-2 mRNA distribution in neonatal and 6-wk-old rats was analyzed by in situ hybridization. In kidneys of newborn rats, the appearance of NaPi-2 protein and mRNA coincided with the development of the brush border (assessed by actin staining) on proximal tubular cells. NaPi-2 was not detectable in the nephrogenic zone or in the outgrowing straight sections of proximal tubules, which lack a brush border. In 13-d-old suckling rats, strong NaPi-2 staining was seen in the BBM of convoluted proximal tubules of all nephron generations. In contrast, in 22-d-old weaned rats, NaPi-2 staining in the BBM of superficial nephrons was weaker than that in the BBM of juxtamedullary nephrons. Western blotting demonstrated that the overall abundance of NaPi-2 protein in the BBM of 22-d-old rats was decreased to approximately 70% of that in 13-d-old rats. In kidneys of 6-wk-old rats, the internephron gradient for NaPi-2 abundance in the BBM corresponded to that in adult rats. The data suggest that the NaPi-2 system in the kidney is fully functional and possesses the capacity for regulation as soon as nephrogenesis is completed. The manifestation of NaPi-2 internephron heterogeneity immediately after weaning might be related to the change in dietary inorganic phosphate content.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Animals, Suckling
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Diet
  • Immunohistochemistry
  • In Situ Hybridization
  • Ion Transport
  • Kidney / growth & development*
  • Kidney / metabolism*
  • Kidney Tubules, Proximal / growth & development
  • Kidney Tubules, Proximal / metabolism
  • Microvilli / metabolism
  • Nephrons / growth & development
  • Nephrons / metabolism
  • Phosphates / administration & dosage
  • Phosphates / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Wistar
  • Sodium / metabolism*
  • Sodium-Phosphate Cotransporter Proteins
  • Sodium-Phosphate Cotransporter Proteins, Type II
  • Symporters*

Substances

  • Carrier Proteins
  • Phosphates
  • RNA, Messenger
  • Sodium-Phosphate Cotransporter Proteins
  • Sodium-Phosphate Cotransporter Proteins, Type II
  • Symporters
  • Sodium