AJP - Cell Physiology, Vol 271, Issue 1 C332-C337, Copyright © 1996 by American Physiological Society
Ca(2+)-dependent nitric oxide release in endothelial but not R3230Ac rat mammary adenocarcinoma cells
R. A. Lindberg, M. W. Dewhirst, B. J. Buckley, C. S. Hughes and A. R. Whorton
Department of Radiation Oncology, Duke University Medical Center, Durham 27710, USA.
We have characterized the ability of several cell types associated with the
microvasculature of solid tumors to release nitric oxide (NO.) in response
to increases in cytosolic Ca2+ concentration ([Ca2+]c). EA.hy926
immortalized human umbilical vein endothelial cells (EC), rat fibroblasts
(RFL), and tumorigenic cells isolated from R3230Ac rat mammary
adenocarcinoma (MaC) were treated with thapsigargin (TG), an inhibitor of
Ca(2+)-ATPase. NO. output was measured via a chemiluminescence detection
system. Baseline NO. output was detectable only for EC. TG caused a
significant increase in EC NO. output that could be blocked with
NG-monomethyl-L-arginine and restored with L-arginine. TG did not stimulate
NO. release from RFL or MaC cells, despite elevating [Ca2+]c in all cells.
A Ca(2+)-dependent isoform of NO synthase (eNOS) was detected by immunoblot
only in EC. These data indicate that EC, but not RFL or MaC, are capable of
Ca(2+)-dependent NO. release and suggest that any Ca(2+)-dependent NO.
release within this tumor is primarily of endothelial (and not tumorigenic
cell) origin.
