AJP - Cell Physiology, Vol 262, Issue 6 C1411-C1417, Copyright © 1992 by American Physiological Society
Flow-induced calcium transients in single endothelial cells: spatial and temporal analysis
R. V. Geiger, B. C. Berk, R. W. Alexander and R. M. Nerem
School of Mechanical Engineering, Georgia Institute of Technology, Atlanta 30332.
Endothelial cells (EC) are uniquely situated to respond to hemodynamic
forces. Because flow-mediated release of endothelial-derived relaxing
factors is associated with increased EC intracellular calcium ([Ca2+]i), we
sought to determine the effects of fluid shear stress on EC [Ca2+]i. Cells
were subjected to flow in parallel-plate flow chambers and glass capillary
tubes, and single cell [Ca2+]i was measured using fura-2. Upon initiation
of flow (shear stress of 30 dyn/cm2), [Ca2+]i increased within 30 s to a
peak value (approximately 4 times basal) and then decreased slowly to a
plateau (approximately 2 times basal) that persisted for greater than 5
min. A striking finding was that the increases in [Ca2+]i were
nonhomogeneous; the nuclear region and a periplasma membrane region were
higher than the cytosol. After flow cessation, the increase in [Ca2+]i
could be elicited repeatedly by resumption of flow. Removing extracellular
Ca2+ did not eliminate the response. In contrast to EC, rat aortic smooth
muscle cells showed no flow-mediated increase in [Ca2+]i. The complexity of
EC [Ca2+]i response to flow suggests regulation of [Ca2+]i by several
mechanisms that may serve a role in both short- and long-term EC responses
to flow.
