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Characterization of Na + /H + exchange activity in cultured rat hippocampal astrocytes
Author(s) -
Pizzonia J.H.,
Ransom B.R.,
Pappas C.A.
Publication year - 1996
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/(sici)1097-4547(19960415)44:2<191::aid-jnr12>3.0.co;2-9
Subject(s) - amiloride , intracellular ph , sodium–hydrogen antiporter , hippocampal formation , gene isoform , chemistry , microbiology and biotechnology , biophysics , intracellular , biochemistry , biology , sodium , endocrinology , organic chemistry , gene
Astrocytes actively maintain their intracellular pH (pH i ) more alkaline than expected by passive distribution of H + . Acid extruding transporters such as the amiloride‐sensitive Na + /H + exchanger (NHE) are necessary for pH regulation. Currently, four mammalian NHEs (NHE1‐NHE4) have been cloned, with a fifth (NHE5) partially cloned. We attempted to determine which isoform(s) of NHE was present in cultured hippocampal astrocytes using amiloride sensitivity and immunospecificity as criteria. In the absence of HCO 3 − , amiloride blocked pH i recovery after an acid load with an IC 50 of ∼3.18 μM, similar to values reported for the amiloride‐sensitive isoforms NHE1 and NHE2. Immunoblotting with a highly specific antibody for NHE1 identified a 100 kDa protein, indicating the presence of NHE1 in whole brain, hippocampus, and cultured hippocampal astrocytes. Further probing for an additional amiloride‐sensitive NHE failed to detect evidence of the presence of NHE4. Surprisingly, application of the potent analog of amiloride, ethylisopropylamiloride (EIPA), caused a reversible alkalinization of pH i , suggesting the presence of an additional acid/base transport mechanism that is EIPA‐sensitive. © 1996 Wiley‐Liss, Inc.