Na+/H+ exchanger isoforms NHE-2 and NHE-1 in inner medullary collecting duct cells. Expression, functional localization, and differential regulation. 1994

M Soleimani, and G Singh, and G L Bizal, and S R Gullans, and J A McAteer
Department of Medicine, Indiana University School of Medicine, Indianapolis.

Recent cloning experiments have identified the existance of four distinct Na+/H+ exchanger isoforms designated as NHE-1, NHE-2, NHE-3, and NHE-4. The cellular distribution, subcellular localization, and regulation of one of these isoforms, NHE-2, in the kidney remains unknown. Northern hybridization showed that NHE-2, along with NHE-1, is expressed in cultured renal medullary collecting duct (mIMCD-3) cells. Acid-stimulated, dimethyl amiloride-sensitive 22Na+ uptake and sodium-dependent pHi recovery occurred only from the basolateral surface of the cells, indicating localization of Na+/H+ exchanger to the basolateral membrane domain. Incubation of IMCD cells in high osmolality media (510 mosm/liter) for 72 h stimulated the Na+/H+ exchanger activity by 59% (p < 0.001). NHE-1 mRNA abundance decreased, whereas NHE-2 mRNA increased in high osmolality media. Incubation of IMCD cells in acid media (pH 7.1) for 48 h did not affect the Na+/H+ exchanger activity compared with control (pH 7.4) (p > 0.05). Northern hybridization, however, indicated that NHE-1 mRNA increased, whereas NHE-2 mRNA decreased in acid media. In conclusion, mIMCD-3 cells express NHE-1 and NHE-2 mRNAs. The cell functional studies in mIMCD-3 cells strongly suggest that NHE-2, along with NHE-1, is expressed in the basolateral membrane domain. They further demonstrate differential regulation of NHE-1 and NHE-2 mRNAs in response to acidosis and high osmolality and suggest that NHE-2 may be involved in volume regulation of IMCD cells.

UI MeSH Term Description Entries
D006982 Hypertonic Solutions Solutions that have a greater osmotic pressure than a reference solution such as blood, plasma, or interstitial fluid. Hypertonic Solution,Solution, Hypertonic,Solutions, Hypertonic
D007679 Kidney Medulla The internal portion of the kidney, consisting of striated conical masses, the renal pyramids, whose bases are adjacent to the cortex and whose apices form prominent papillae projecting into the lumen of the minor calyces. Kidney Papilla,Kidney Medullas,Kidney Papillas,Medulla, Kidney,Medullas, Kidney,Papilla, Kidney,Papillas, Kidney
D007685 Kidney Tubules, Collecting Straight tubes commencing in the radiate part of the kidney cortex where they receive the curved ends of the distal convoluted tubules. In the medulla the collecting tubules of each pyramid converge to join a central tube (duct of Bellini) which opens on the summit of the papilla. Kidney Collecting Ducts,Kidney Collecting Duct,Collecting Duct, Kidney,Collecting Ducts, Kidney
D007700 Kinetics The rate dynamics in chemical or physical systems.
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012333 RNA, Messenger RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm. Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated
D015152 Blotting, Northern Detection of RNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES. Northern Blotting,Blot, Northern,Northern Blot,Blots, Northern,Blottings, Northern,Northern Blots,Northern Blottings
D015870 Gene Expression The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION. Expression, Gene,Expressions, Gene,Gene Expressions

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