Angiotensin ii mediates a sustained rise in nuclear and cytoplasmic
calcium via multiple receptor subtypes.
Munzenmaier, Diane H., and Andrew S. Greene.
Department of Physiology, Medical College of Wisconsin, Milwaukee,
Wisconsin 53226
APStracts 2:0067H, 1995.
Alterations in nuclear calcium levels in response to ANG II may play
an important role in the trophic actions of ANG II. This study
utilized confocal microscopy and nuclear staining to test the
hypothesis that both nuclear and cytoplasmic calcium levels are
altered in response to ANG II stimulation of freshly dissociated
aortic smooth muscle cells. Cells were loaded with the calcium
indicator fluo 3 (fluo 3-AM) and the calcium response to ANG II
stimulation was analyzed over time with a laser-scanning confocal
microscope. Additionally, the ratiometric calcium indicator fura 2
(fura 2-AM) and conventional fluorescence microscopy were used to
verify these observations. Results show that basal nuclear calcium
exceeds cytoplasmic calcium in these cells. Stimulation by ANG II
induces a sustained rise (separate from the rapid transient) in both
nuclear and cytoplasmic calcium in excess of 20 minutes in duration.
This rise was blockable by either the AT1 receptor antagonist DuP 753
or by the AT2 antagonist PD 123319. Thus, ANG II stimulates a
sustained rise in nuclear calcium by a mechanism which necessitates
activation of both AT1 and AT2 receptors.
Received 31 October 1994; accepted in final form 21 February
1995.
APS Manuscript Number H970-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.