Extracellular ATP increases NH4+ permeability in human lymphocytes by opening a P2Z purinoceptor operated ion channel

• Published in: Biochemical and biophysical research communications Vol. 202; no. 3; pp. 1511 - 1516
• Main Authors: Chen, J R, Jamieson, G P, Wiley, J S
• Format: Journal Article
• Language: English
• Published: United States 15.08.1994
• Subjects: Adenosine Triphosphate - physiology; Amiloride - analogs & derivatives; Amiloride - pharmacology; Amines - pharmacology; Biological Transport; Calcium - metabolism; Cell Membrane Permeability; Fluoresceins; Fluorescent Dyes; Humans; Hydrogen-Ion Concentration; Ion Channels - physiology; Lymphocytes - metabolism; Oxidation-Reduction; Quaternary Ammonium Compounds - metabolism; Receptors, Purinergic - physiology
• ISSN: 0006-291X
• DOI: 10.1006/bbrc.1994.2102

The permeability of lymphocytes to NH4+ was examined by measuring intracellular pH using the fluorescent pH-sensitive dye BCECF. Addition of 20 mM NH4Cl produced a rapid phase of alkalinization. This was followed by a slow return to resting pHi due to NH4+ influx. The rate of NH4+ was increased many fold by extracellular ATP and the increment showed features consistent with NH4+ being a permeant for the P2Z purinoceptor operated ion channel. Cytosolic pH measurements showed monomethylammonium+ and dimethylammonium+ were also permeants, but trimethylammonium+ (69 Dalton) was excluded by this channel. Since our previous data showed ethidium+ (314 Dalton) is a permeant it appears that molecular conformation rather than molecular weight determines entry of cationic solutes through the channel.