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Kinetics of cell lysis, dye uptake and permeability changes in cells expressing the rat P2X 7 receptor
Author(s) -
Virginio C.,
MacKenzie A.,
North R. A.,
Surprenant A.
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.0335m.x
Subject(s) - extracellular , biophysics , intracellular , chemistry , lysis , sodium , permeability (electromagnetism) , permeation , membrane , receptor , kinetics , membrane potential , membrane permeability , cell membrane , biochemistry , biology , physics , organic chemistry , quantum mechanics
1 Extracellular ATP acting on P2X 7 receptors opens a channel permeable to small cations, creates an access pathway for the entry of larger molecular weight dyes, and causes cell death. We used whole‐cell recording and fluorescence microscopy to measure the time courses of ionic currents, uptake of the propidium dye YO‐PRO‐1, and membrane disruption, in human embryonic kidney (HEK293) cells expressing the rat P2X 7 receptor. 2 The ATP analogue 2′,3′‐ O ‐(benzoyl‐4‐benzoyl)‐ATP (30 μ m ) induced membrane blebbing within 30‐40 s of sustained application; this was 5‐10 times slower when extracellular sodium was replaced by larger cations. 3 Fluorescence of YO‐PRO‐1 was detectable within 3 s, and the uptake reached a steady rate within 10‐20 s; YO‐PRO‐1 uptake was greatly enhanced by removing extracellular sodium. 4 Electrophysiological measurements of current reversal potentials with intracellular sodium and extracellular cations of different sizes showed that the ionic channel progressively dilated during 10‐20 s to a diameter greater than 1 nm (10 Å). With short agonist applications (3‐5 s) the pore dilatation and YO‐PRO‐1 uptake were reversible and repeatable. 5 Polyethylene glycols having molecular weights ≥ 5000 blocked the increase in cation permeability, YO‐PRO‐1 uptake and membrane blebbing. 6 We conclude that maximum P2X 7 receptor activation causes an exponential dilatation of the ion channel with a time constant of 25 s to a final diameter of 3‐5 nm from an initial minimum pore diameter of 0.8 nm.