The calcium responses of endothelial cell monolayers subjected to
pulsatile and steady laminar flow differ.
Helmlinger, Gabriel, Bradford C. Berk, and Robert M. Nerem.
School of Mechanical Engineering, Georgia Institute of Technology,
Atlanta GA, and Division of Cardiology, University of Washington,
Seattle WA
APStracts 2:0137C, 1995.
The vascular endothelium is the primary transducer of hemodynamically
-imposed mechanochemical events. In this study, we measured the
intracellular free calcium concentration ([Ca2+]i) using the
fluorescent probe Fura-2 and ratiometric digital imaging, in cultured
bovine aortic endothelial cells (BAECs) subjected to various laminar
flow patterns. These were: steady shear stress (0.2 to 70 dyn/cm2)
and three types of sinusoidal pulsatile shear stress (non-reversing:
40+/-20 dyn/cm2; reversing: 20+/-40 dyn/cm2; and purely oscillatory:
0+/-20 dyn/cm2; flow frequencies: 0.4, 1.0, and 2.0 Hz) in a serum
-containing medium. The most dramatic finding was failure of a purely
oscillatory flow to increase [Ca2+]i in BAEC monolayers. In contrast,
steady flow, as well as non-reversing and reversing pulsatile flows
increased [Ca2+]i. The dynamics of the response were dependent on the
flow pattern. Both internal Ca2+ release and extracellular Ca2+ entry
were involved in these [Ca2+]i increases. Also, switching from either
a steady, non-reversing pulsatile, or reversing pulsatile flow back
to a static condition resulted in a [Ca2+]i increase. However,
switching from an oscillatory flow to a static condition did not
induce any changes in average [Ca2+]i. This study shows that ECs are
able to sense different flow environments in terms of [Ca2+]i
signaling and is relevant to further studies of the influence of
hemodynamic forces on vascular pathophysiology.
Received 1 July 1994; accepted in final form 6 February 1995.
APS Manuscript Number C378-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.