ATP- and UTP-induced currents in macrophages and macrophage polykaryons.
We have investigated the currents induced by extracellular ATP (ATPo), extra-cellular UTP, and other related compounds in macrophages. At potentials of -20 to -60 mV, a typical response to ATPo puffs consists of a fast-activating inward current followed by a transient outward current. The phenomenon lasts 5-20 s, but for sustained exposure to ATP the inward current persists for up to 10 min (our longest recording time). Both currents are inhibited by Mg2+, suggesting that the phenomenon is mediated by ATP4-. The outward current can be ascribed to a Ca(2+)-dependent K+ conductance, and release of Ca2+ from intracellular stores is at least in part responsible for this current. The inward current has a reversal potential of approximately 0 mV, and it is nonspecific for monovalent cations. UTP, a nucleotide that induces an increase in the cytoplasmic concentration of free Ca2+ but does not permeabilize macrophages, and ATP-gamma-S can also induce inward and outward current similar to those described for ATP, but higher doses are required. Adenosine and AMP produce no detectable effect, whereas ADP induces a small outward current. The implications of these results to the phenomenon of ATPo-induced permeabilization of macrophage membranes to large molecules are discussed.
Albuquerque
C
C
Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
Oliveira
S M
SM
Coutinho-Silva
R
R
Oliveira-Castro
G M
GM
Persechini
P M
PM
D000241:Adenosine / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D004558:Electric Stimulation; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D008536:Meglumine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011803:Quinine / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology*
D005971:Glutamates; D015221:Potassium Channels; C022571:adenosine 5'-O-(3-thiotriphosphate); D018698:Glutamic Acid; D000249:Adenosine Monophosphate; D004533:Egtazic Acid; D000244:Adenosine Diphosphate; D008536:Meglumine; D000255:Adenosine Triphosphate; D011803:Quinine; D008274:Magnesium; D000241:Adenosine; D002118:Calcium; D014544:Uridine Triphosphate