title: Growth-related renal type II Na/Pi cotransporter.
abstract: Growth is critically dependent on the retention of a variety of nutrients. The kidney contributes to this positive external balance. In the present study, we isolated a cDNA from the human and rat kidney that encodes a growth-related Na(+)-dependent inorganic phosphate (P(i)) cotransporter (type IIc). Microinjection of type IIc cRNA into Xenopus oocytes demonstrated sodium-dependent P(i) cotransport activity. Affinity for P(i) was 0.07 mm in 100 mm Na(+). The transport activity was dependent on extracellular pH. In electrophysiological studies, type IIc Na/P(i) cotransport was electroneutral, whereas type IIa was highly electrogenic. In Northern blotting analysis, the type IIc transcript was only expressed in the kidney and highly in weaning animals. In immunohistochemical analysis, the type IIc protein was shown to be localized at the apical membrane of the proximal tubular cells in superficial and midcortical nephrons of weaning rat kidney. Hybrid depletion experiments suggested that type IIc could function as a Na/P(i) cotransporter in weaning animals, but its role is reduced in adults. The finding of the present study suggest that the type IIc is a growth-related renal Na/P(i) cotransporter, which has a high affinity for P(i) and is electroneutral.
authors.affiliation: Department of Nutrition, School of Medicine, Tokushima University, Kuramoto-Cho 3, Tokushima City 770-8503, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Segawa
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kaneko
authors.forename: Akira
authors.initials: A
authors.lastname: Takahashi
authors.forename: Masashi
authors.initials: M
authors.lastname: Kuwahata
authors.forename: Mikiko
authors.initials: M
authors.lastname: Ito
authors.forename: Ichiro
authors.initials: I
authors.lastname: Ohkido
authors.forename: Sawako
authors.initials: S
authors.lastname: Tatsumi
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Miyamoto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D015152:Blotting, Northern; D015153:Blotting, Western; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D018075:RNA, Complementary / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017386:Sequence Homology, Amino Acid; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters / Q000378:metabolism* / Q000502:physiology*; D013997:Time Factors; D014018:Tissue Distribution; D014981:Xenopus
chemical_list: D018076:DNA, Complementary; D016376:Oligonucleotides, Antisense; D010455:Peptides; D018075:RNA, Complementary; D012333:RNA, Messenger; C493554:SLC34A1 protein, human; C493556:Slc34a1 protein, rat; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters