title: Age-dependent regulation of rat intestinal type IIb sodium-phosphate cotransporter by 1,25-(OH)(2) vitamin D(3).
abstract: The current studies were designed to characterize type IIb sodium-inorganic phosphate (P(i)) cotransporter (NaP(i)-IIb) expression and to assess the effect of 1,25-(OH)(2) vitamin D(3) on NaP(i)-IIb gene expression during rat ontogeny. Sodium-dependent P(i) absorption by intestinal brush-border membrane vesicles (BBMVs) decreased with age, and NaP(i)-IIb gene expression also decreased proportionally with age. 1,25-(OH)(2) vitamin D(3) treatment increased intestinal BBMV P(i) absorption by approximately 2.5-fold in suckling rats and by approximately 2.1-fold in adult rats. 1,25-(OH)(2) vitamin D(3) treatment also increased NaP(i)-IIb mRNA abundance by approximately 2-fold in 14-day-old rats but had no effect on mRNA expression in adults. Furthermore, in rat intestinal epithelial (RIE) cells, 1,25-(OH)(2) vitamin D(3) increased NaP(i)-IIb mRNA abundance, an effect that was abolished by actinomycin D. Additionally, human NaP(i)-IIb gene promoter activity in transiently transfected RIE cells showed approximately 1.6-fold increase after 1,25-(OH)(2) vitamin D(3) treatment. In conclusion, we demonstrate that the age-related decrease in intestinal sodium-dependent P(i) absorption correlates with decreased NaP(i)-IIb mRNA expression. Our data also suggest that the effect of 1,25-(OH)(2) vitamin D(3) on NaP(i)-IIb expression is at least partially mediated by gene transcription in suckling rats.
authors.affiliation: Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona Health Sciences Center, 1501 N. Campbell Ave., Tucson, AZ 85724, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Xu
authors.forename: Liqun
authors.initials: L
authors.lastname: Bai
authors.forename: James F
authors.initials: JF
authors.lastname: Collins
authors.forename: Fayez K
authors.initials: FK
authors.lastname: Ghishan
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050608:Sodium-Phosphate Cotransporter Proteins; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D027981:Symporters / Q000235:genetics / Q000378:metabolism*
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D012333:RNA, Messenger; C493557:SLC34A2 protein, human; C493559:Slc34a2 protein, rat; D050608:Sodium-Phosphate Cotransporter Proteins; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D027981:Symporters; D003609:Dactinomycin; D002117:Calcitriol