Angiotensin ii receptor stimulation of cytosolic calcium
concentration in cultured renal resistance arterioles.
Zhu, Zhiming, and William J. Arendshorst.
Department of Physiology, University of North Carolina at Chapel
Hill, Chapel Hill, NC 27599-7545
APStracts 3:0165F, 1996.
This study provides an initial characterization of basic morphological
properties of cultures of vascular smooth muscle cells (SMC) from rat
preglomerular resistance vessels and of the functional coupling of
angiotensin II (ANG II) receptors to cytosolic free calcium
concentration ([Ca2+]i (fura-2 fluorescence photometry). Renal SMC
were isolated from interlobular arteries and afferent arterioles (
< 50 [mu]m) using an iron oxide-sieving method and compared
with rat aortic-SMC cultured under similar conditions. Quiescent
monolayers maintained uniform morphology and [Ca2+]i signaling
profile between passages 2 - 10. Arteriolar and aortic SMC were
spindle-shaped and expressed smooth muscle specific [alpha]-actin and
myosin heavy chains SM-1 and SM-2. ANG II caused a rapid increase in
[Ca2+]i , followed by a sustained plateau phase at 50-60% of the peak
value. The initial maximum [Ca2+]i responses were dose-dependent and
of similar magnitude in renal arteriolar- and aortic-SMC. ANG II (10
-7 M) increased [Ca2+]i from 50 to 240 nM in arteriolar- and from 57
to 201 nM in aortic-SMC (P < 0.001 for both). Inhibition of
ANG II effects on [Ca2+]i revealed significant signaling through
distinct receptor AT subtypes (losartan and PD-123319 sensitive) in
renal arteriolar-SMC. In contrast, only losartan was effective in
aortic SMC. The AT2 receptor ligand CGP-42112 had no effect in either
vessel type. Our results demonstrate that cultured arteriolar SMC
have anatomical similarities to aortic SMC and functional differences
in AT receptor signaling in response to ANG II. This novel
preparation should provide a useful approach to investigate cellular
mechanisms concerning receptor coupling to signaling pathways
involved in vascular reactivity of arteriolar SMC in the
microcirculation in general and the kidney in particular.
Received 20 March 1996; accepted in final form 5 September 1996.
APS Manuscript Number F95-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996