Smooth muscle cells contract in response to fluid flow via a Ca2+-independent signaling mechanism.
Smooth muscle cells (SMC) are exposed to fluid shear stress because of transmural (interstitial) flow across the arterial wall. This shear stress may play a role in the myogenic response and flow-mediated vasomotion. We, therefore, examined the effects of fluid flow on contraction of rat aortic SMC. SMC that had been serum-starved to induce a contractile phenotype were plated on quartz slides and exposed to controlled shear stress levels in a flow chamber. The area of the cells was quantified, and reduction in the cell area was reported as contraction. At 25 dyn/cm(2), significant area reduction was apparent 3 min after the onset of flow and exceeded 30% at 30 min. At 1 dyn/cm(2), significant contraction was not observed at 30 min. The threshold for significant shear-induced contraction appeared to be 11 dyn/cm(2). The signal transduction mechanism was studied at 25 dyn/cm(2). Intracellular calcium was imaged by using the calcium-sensitive fluorescent dye fura 2-AM. There was no detectable change in intracellular calcium during 10 min of exposure to shear stress, even though the cells displayed a significant calcium response to thapsigargin, calcium ionophore, and KCl. Further studies using pathway inhibitors provided evidence that the most important signal transduction pathway mediating calcium-independent contraction in response to fluid flow is the Rho-kinase pathway, although there was a suggestion that protein kinase C plays a secondary role.
Civelek
Mete
M
Biomolecular Transport Dynamics Laboratory, Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Ainslie
Kristy
K
Garanich
Jeff S
JS
Tarbell
John M
JM
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology; D001783:Blood Flow Velocity / Q000502:physiology; D001905:Botulinum Toxins / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D018715:Microscopy, Video; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical
D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; C070515:bisindolylmaleimide I