Exposure of human neutrophils to exogenous nucleotides causes elevation in
intracellular calcium, transmembrane calcium fluxes, and an alteration of a
cytosolic factor resulting in enhanced superoxide production in response to
FMLP and arachidonic acid
RA Axtell, RR Sandborg, JE Smolen, PA Ward and LA Boxer
Department of Pediatrics, University of Michigan, Ann Arbor 48109-0238.
Exposure of human neutrophils to micromolar concentrations of both
hydrolyzable and nonhydrolyzable purine nucleotides caused the generation
of transient rises in intracellular calcium (Ca2+), Ca2+ fluxes across the
membrane, and primed the cells for enhanced production of superoxide (O2-)
when subsequently exposed to agonists such as FMLP and arachidonic acid.
The neutrophils were most sensitive to adenosine triphosphate (ATP) and
ATP-gamma-S, which produced Ca2+ transients and enhanced O2- production at
concentrations as low as 1 to 5 mumol/L, with a doubling of O2- generation
at 25 to 50 mumol/L. Adenosine diphosphate (ADP), guanosine triphosphate
(GTP), and 5'- adenylylimidodiphosphate (AMP-PNP) required approximately
10-fold higher concentrations to cause similar effects. Adenosine did not
cause Ca2+ fluxes or a Ca2+ transient and was inhibitory of O2- production.
There was a strong correlation between a nucleotide's ability to generate a
Ca2+ response and its ability to enhance O2- generation. Nitrogen
cavitation and subcellular fractionation of the neutrophils after a brief
exposure to ATP, ATP-gamma-S, and AMP-PNP revealed that the enhanced O2-
generating capacity was stable and detectable in a cell-free assay system.
By combining variously treated cytosolic and membrane fractions, it was
found that the enhanced O2- production was attributable to a modification
of a component(s) of the cytosol.
Volume 75,
Issue 6,
pp. 1324-1332,
03/15/1990
Copyright © 1990 by The American Society of Hematology
