Publications & Reports

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

J R Chen, G P Jamieson, J S Wiley
Department of Haematology, Austin Hospital, Heidelberg, Vic., Australia.


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.


  • Journal: Biochemical and Biophysical Research Communications
  • Published: 15/08/1994
  • Volume: 202
  • Issue: 3
  • Pagination: 1511-1516