title: Effects of angiotensin II on NaPi-IIa co-transporter expression and activity in rat renal cortex.
abstract: The kidney plays a major role in reabsorption of phosphate with the majority occurring in the proximal tubule (PT). The type IIa sodium-phosphate co-transporter (NaPi-IIa) is the main player in PT. The purpose of current study was to determine the effect of angiotensin II (A-II) on membrane expression of NaPi-IIa in the rat renal cortex. A-II (500 ng/kg/min) was chronically infused into the Sprague-Dawley rats by miniosmotic pump for 7 days. The arterial pressure and circulating plasma A-II level along with urine output were markedly increased in A-II rats. There was diuresis but no natriuresis. The phosphate excretion increased sevenfold on day 4 and 5.7-fold on day 7. There was no change in Na-dependent Pi uptake in brush-border membrane (BBM) vesicles between A-II-treated group and control on day 4, however, there was a 43% increase on day 7. Western blot analysis of NaPi-IIa protein abundance showed a parallel pattern: no change after 4 days of treatment and a 48% increase after 7 days of treatment. However, Northern blot analysis of cortical RNA showed no change in NaPi-IIa mRNA abundance on day 7. A-II stimulation of Na/Pi co-transport activity is a result of increases in the expression of BBM NaPi-IIa protein level and that stimulation is most likely mediated by posttranscriptional mechanisms.
authors.affiliation: Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona Health Sciences Center, 1501 N. Campbell Avenue, Tucson, AZ 85724, USA.
authors.forename: Liping
authors.initials: L
authors.lastname: Xu
authors.forename: Mehul P
authors.initials: MP
authors.lastname: Dixit
authors.forename: Rongji
authors.initials: R
authors.lastname: Chen
authors.forename: Naznin M
authors.initials: NM
authors.lastname: Dixit
authors.forename: James F
authors.initials: JF
authors.lastname: Collins
authors.forename: Fayez K
authors.initials: FK
authors.lastname: Ghishan
mesh_terms: D000804:Angiotensin II / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D004231:Diuresis / Q000187:drug effects; D005919:Glomerular Filtration Rate / Q000187:drug effects; D007260:Infusion Pumps; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D014556:Urine / Q000737:chemistry
chemical_list: D012333:RNA, Messenger; C493556:Slc34a1 protein, rat; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters; D000804:Angiotensin II