Calcium-dependent nitric oxide release in ea.hy926 endothelial but
not r3230ac rat mammary adenocarcinoma cells.
Lindberg, Robert A., Mark W. Dewhirst, Barbara J. Buckley, Christine
S. Hughes, and A. Richard Whorton.
Departments of Radiation Oncology, Medicine and Pharmacology, Duke
University Medical Center, Durham, NC 27710, and 3College of
Veterinary Medicine, North Carolina State University, Raleigh, NC
27606
APStracts 3:0038C, 1996.
We have characterized the ability of several cell types associated
with the microvasculature of solid tumors to release nitric oxide
(NOx) in response to the mobilization of cytosolic calcium ([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 Ca2+ ATPase. NOx output was measured via a
chemiluminescence detection system. Baseline NOx output was
detectable only for EC. TG caused a significant increase in EC NOx
output, which could be blocked with NG-monomethyl L-arginine and
restored with L-arginine. TG did not stimulate NOx release from RFL
or MaC cells, despite elevating [Ca2+]c in all cells. A Ca2+
-dependent isoform of NO synthase (eNOS) was detected by immunoblot
only in EC. These data indicate that EA.hy926 endothelial cells, but
not rat fibroblasts or rat mammary adenocarcinoma cells, are capable
of Ca2+-dependent NOx release, and suggest that any Ca2+-dependent
NOx release within this tumor is primarily of endothelial (and not
tumorigenic cell) origin.
Received 7 August 1995; accepted in final form 11 January 1996.
APS Manuscript Number C487-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 February 96