Volume 14, No 5, Oct 2004

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 14 Issue 5, October 2004: 379-388

ORIGINAL ARTICLES

Spontaneous Ca²⁺ oscillations in subcellular compartments of vascular smooth muscle cells rely on different Ca²⁺ pools

Olesya D. Fedoryak¹, Yvonne Searls^1,2, Irina V. Smirnova¹, Douglas M. Burns³, Lisa Stehno-Bittel^1,2*

¹Departments of Physical Therapy and Rehabilitation Sciences, University of Kansas Medical Center, Kansas City, KS 66160, USA.
²Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160,USA.
³VA Medical Center, Kansas City, MO 64128,USA Correspondence: Lisa Stehno-Bittel(lbittel@kumc.edu)

Spontaneous Ca²⁺ oscillations in vascular smooth
muscle cells have been modeled using a single Ca²⁺ pool. This
report describes spontaneous Ca²⁺ oscillations dependent on
two separate Ca²⁺ sources for the nuclear versus cytoplasmic
compartments. Changes in free intracellular Ca²⁺ were monitored
with ratiometric Ca²⁺- fluorophores using confocal microscopy.
On average, spontaneous oscillations developed in 79% of rat aortic smooth
muscle cells that were synchronous between the cytoplasm and nucleus.
Reduction of extracellular Ca²⁺ (< 1 mM) decreased the frequency
and amplitude of the cytoplasmic oscillations with 48% of the oscillations
asynchronous between the nuclear and cytoplasmic compartments. Similar
results were obtained with the Ca²⁺ channel blockers, nimodipine
and diltiazem. Arg-vasopressin (AVP) induced a rapid release of intracellular
Ca²⁺ stores that was greater in the nuclear compartment (4.20
± 0.23 ratio units, n = 56) than cytoplasm (2.54 ± 0.28) in
cells that had spontaneously developed prior oscillations. Conversely,
cells in the same conditions lacking oscillations had a greater AVP-induced
Ca²⁺ transient in the cytoplasm (4.99 ± 0.66, n = 17)
than in the nucleus (2.67 ± 0.29). Pre-treatment with Ca²⁺
channel blockers depressed the AVP responses in both compartments with
the cytoplasmic Ca²⁺ most diminished. Depletion of internal
Ca²⁺ stores prior to AVP exposure blunted the nuclear response,
mimicking the response of cells that lacked prior oscillations. Spontaneous
oscillating cells had a greater sarcoplasmic reticulum network than cells
that did not oscillate. We propose that spontaneous nuclear oscillations
rely on perinuclear sarcoplasmic reticulum stores, while the cytoplasmic
oscillations rely on Ca²⁺ influx.

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