PMID- 10027934 OWN - NLM STAT- MEDLINE DCOM- 19990416 LR - 20131121 IS - 0085-2538 (Print) IS - 0085-2538 (Linking) VI - 55 IP - 3 DP - 1999 Mar TI - Effects of phosphate intake on distribution of type II Na/Pi cotransporter mRNA in rat kidney. PG - 976-83 AB - BACKGROUND: Renal phosphate (Pi) reabsorption is regulated by dietary Pi intake, as well as in other ways. Changes in Pi reabsorption are associated with the modulation of sodium/Pi cotransporter type II (NaPi-2) protein abundance in the brush border membrane (BBM) of proximal tubules (PTs) and of renal NaPi-2 mRNA levels. In this study, we address whether the NaPi-2 protein and NaPi-2 mRNA distribution patterns in the renal cortex vary in parallel with changes of dietary Pi intake. METHODS: We investigated in cryosections of perfusion-fixed rat kidneys by in situ hybridization (ISH) and immunohistochemistry (IHC) the distribution patterns of NaPi-2 mRNA and of NaPi-2 protein one week, two hours, and four hours after changes in dietary Pi intake. RESULTS: NaPi-2 mRNA and NaPi-2 protein were present in PTs exclusively. In rats adapted to one week of high Pi intake, signals for NaPi-2 mRNA and NaPi-2 protein in cortical PTs were weak, except in the convoluted parts of PTs of juxtamedullary nephrons. After one week of low Pi intake, the ISH and IHC signals for NaPi-2 were high in PT segments in all cortical levels. The switch from a chronic high to a low Pi intake within two and four hours induced no increase and a slight increase, respectively, in the NaPi-2 mRNA signal in PTs of midcortical and of superficial nephrons, whereas in the BBM of these nephrons, NaPi-2 protein was markedly up-regulated. Two and four hours after switching from low to high Pi intake, the overall high ISH signal for NaPi-2 mRNA was unchanged, whereas NaPi-2 protein staining was drastically down-regulated in the BBM of PTs from superficial and midcortical nephrons. CONCLUSIONS: The marked changes in NaPi-2 protein abundance in the BBM, following altered dietary Pi intake, precede corresponding changes at the RNA level by several hours. Thus, the early adaptation to altered Pi intake involves mRNA-independent mechanisms. The up- or down-regulation of NaPi-2 protein abundance in the BBM and NaPi-2 mRNA in PT affects mainly midcortical and superficial nephrons. FAU - Ritthaler, T AU - Ritthaler T AD - Institutes of Anatomy and Physiology, University of Zurich-Irchel, Zurich, Switzerland. FAU - Traebert, M AU - Traebert M FAU - Lotscher, M AU - Lotscher M FAU - Biber, J AU - Biber J FAU - Murer, H AU - Murer H FAU - Kaissling, B AU - Kaissling B LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't PL - United States TA - Kidney Int JT - Kidney international JID - 0323470 RN - 0 (Carrier Proteins) RN - 0 (Phosphates) RN - 0 (RNA, Messenger) RN - 0 (Sodium-Phosphate Cotransporter Proteins) RN - 0 (Sodium-Phosphate Cotransporter Proteins, Type II) RN - 0 (Symporters) RN - 9NEZ333N27 (Sodium) SB - IM MH - Animals MH - Carrier Proteins/classification/*genetics/metabolism MH - Diet MH - Immunohistochemistry MH - In Situ Hybridization MH - Kidney/*metabolism MH - Male MH - Phosphates/*administration & dosage/metabolism MH - RNA, Messenger/*genetics/*metabolism MH - Rats MH - Rats, Wistar MH - Sodium/metabolism MH - Sodium-Phosphate Cotransporter Proteins MH - Sodium-Phosphate Cotransporter Proteins, Type II MH - *Symporters MH - Time Factors EDAT- 1999/02/23 00:00 MHDA- 1999/02/23 00:01 CRDT- 1999/02/23 00:00 PHST- 1999/02/23 00:00 [pubmed] PHST- 1999/02/23 00:01 [medline] PHST- 1999/02/23 00:00 [entrez] AID - S0085-2538(15)46044-2 [pii] AID - 10.1046/j.1523-1755.1999.055003976.x [doi] PST - ppublish SO - Kidney Int. 1999 Mar;55(3):976-83. doi: 10.1046/j.1523-1755.1999.055003976.x.