J. Suvatne et al., Flow-induced expression of endothelial Na-K-Cl cotransport: dependence on K+ and Cl- channels, AM J P-CELL, 280(1), 2001, pp. C216-C227
Steady laminar shear stress has been shown previously to markedly increase
Na-K-Cl cotransporter mRNA and protein in human umbilical vein endothelial
cells and also to rapidly increase endothelial K+ and Cl- channel conductan
ces. The present study was done to evaluate the effects of shear stress on
Na-K-Cl cotransporter activity and protein expression in bovine aortic endo
thelial cells (BAEC) and to determine whether changes in cotransporter expr
ession may be dependent on early changes in K+ and Cl- channel conductances
. Confluent BAEC monolayers were exposed in a parallel-plate flow chamber t
o either steady shear stress (19 dyn/cm(2)) or purely oscillatory shear str
ess (0 +/- 19 dyn/cm(2)) for 6-48 h. After shearing, BAEC monolayers were a
ssessed for Na-K-Cl cotransporter activity or were subjected to Western blo
t analysis of cotransporter protein. Steady shear stress led to a 2- to 4-f
old increase in BAEC cotransporter protein levels and a 1.5- to 1.8-fold in
crease in cotransporter activity, increases that were sustained over the lo
ngest time periods studied. Oscillatory flow, in contrast, had no effect on
cotransporter protein levels. In the presence of flow-sensitive K+ and Cl-
channel pharmacological blockers, the steady shear stress-induced increase
in cotransporter protein was virtually abolished. These results suggest th
at shear stress modulates the expression of the BAEC Na-K-Cl cotransporter
by mechanisms that are dependent on flow-activated ion channels.