Fluid shear stress modulates cytosolic free calcium in vascular endothelial cells.
Cytosolic free Ca2+ concentration ([Ca2+]i) was monitored in single and groups of fura-2-loaded bovine aortic endothelial cells (BAEC) during exposure to laminar fluid shear stress. Application of a step increase in shear stress from 0.08 to 8 dyn/cm2 to confluent BAEC monolayers resulted in a transient increase in [Ca2+]i, which attained a peak value in 15-40 s, followed by a decline to baseline within 40-80 s. The magnitude of the [Ca2+]i responses increased with applied shear stress over the range of 0.2-4 dyn/cm2 and reached a maximum at greater than 4 dyn/cm2. Transient oscillations in [Ca2+]i with gradually diminishing amplitude were observed in individual cells subjected to continuous high shear stress. Elimination of extracellular Ca2+ with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, blockade of Ca2+ entry with lanthanum, depolarization of the cell membrane with high K+, and preconditioning of BAEC in steady laminar flow had little effect on the [Ca2+]i response. In the presence of ATP or ADP, application of shear stress caused repetitive oscillations in [Ca2+]i in single BAEC, whose frequency was dependent on both agonist concentration and the magnitude of applied shear stress. However, apyrase, an ATPase and ADPase, did not inhibit the shear-induced [Ca2+]i responses in standard medium (no added ATP or ADP), suggesting that the shear-induced [Ca2+]i response is not due to ATP released by endothelial cells.
Shen
J
J
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge 02139.
Luscinskas
F W
FW
Connolly
A
A
Dewey
C F
CF
Gimbrone
M A
MA
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001081:Apyrase / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D008564:Membrane Potentials; D009994:Osmolar Concentration; D013314:Stress, Mechanical
D000255:Adenosine Triphosphate; D001081:Apyrase; D002118:Calcium