Characterization of Na+/H+ exchange activity in cultured rat hippocampal astrocytes

✍ Scribed by J.H. Pizzonia; B.R. Ransom; C.A. Pappas

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 730 KB
• Volume: 44
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/(sici)1097-4547(19960415)44:2<191::aid-jnr12>3.0.co;2-9

✦ Synopsis

Astrocytes actively maintain their intracellular pH (pH,) 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 (NHES) 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 HC0,-, amiloride blocked pH, recovery after an acid load with an IC,, of -3.18 pM, similar to values reported for the amiloride-sensitive isoforms NHEl and NHE2. Immunoblotting with a highly specific antibody for NHEl identified a 100 kDa protein, indicating the presence of NHEl 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 pHi, suggesting the presence of an additional acidbase transport mechanism that is EIPA-sensitive.