Sk. Kong et al., THE NITRIC-OXIDE DONOR, SODIUM-NITROPRUSSIDE, INCREASED INTRANUCLEAR AND CYTOSOLIC-FREE CALCIUM-CONCENTRATION IN SINGLE PU5-1.8 CELLS, Biochemical and biophysical research communications, 199(1), 1994, pp. 234-240
In the present study, the effect of sodium nitroprusside (SNP), a nitr
ic oxide (NO) releasing agent, on the intracelluar free calcium concen
tration ([Ca2+]i) was studied. Our results demonstrate that SNP could
increase [Ca2+]i in single PU5-1.8 cells, a murine macrophage cell lin
e, as determined by confocal laser scanning microscope with calcium gr
een-1 fluorescent probe. In the presence of hemoglobin, a NO scavenger
, the effect of SNP on the Ca2+ level was suppressed. Our data also sh
ow that the intranuclear Ca2+ ([Ca2+]n) was always higher than those i
n cytosol. Stimulation of cells with 1mM SNP induced an immediate incr
ease of [Ca2+]n with a delayed rise of cytosolic Ca2+ ([Ca2+]c). Inter
estingly, when cells were subsequently treated with 2mM SNP, an increa
se of [Ca2+]c with a similar pattern to the rise [Ca2+]n was observed.
In Ca2+-free buffer, SNP also raised the [Ca2+]n and [Ca2+]c. When Ca
2+ was added to the buffer, a second peak of [Ca2+]n and several spike
s of [Ca2+]c were observed. These results thus indicate that 1) NO may
increase both [Ca2+]n and [Ca2+]c in PU5-1.8 cells; 2) the increase o
f [Ca2+]n requires both internal and external Ca2+. Moreover, the dive
rse responses in these cells suggest that the regulation of Ca2+ in th
ese areas may be different. (C) 1994 Academic Press, Inc.