PROSTACYCLIN PRODUCTION BY CULTURED ENDOTHELIAL CELL MONOLAYERS EXPOSED TO STEP INCREASES IN SHEAR-STRESS

Abstract

While fluid shear stress is an important cardiovascular factor in vivo, it has generally been ignored in in-vitro assays of endothelial cell function. The influence of shear stress on the production of prostacyclin by confluent monolayers of bovine aortic endothelial cells placed in a lucite flow chamber and exposed to flowing culture medium at constant shear stress at 37.degree. C and pH 7.4 was quantified. Continuous inverted-phase microscopy (.times.300) of the monolayers showed no significant contraction or detachment of cells under these conditions. Step increases in shear stress from 0 to 14 dyne/cm2 caused rapid rises in prostacyclin production, from a baseline (n = 4) of 0.17 .+-. 0.062 ng/cm2 .cntdot. min (mean .+-. SEM) to peak values within 2 min, followed by a decline over several minutes. Peak prostacyclin production increased (P < 0.005) with shear stress, from 0.60 .+-. 0.13 ng/cm2 .cntdot. min at 0.9 dyne/cm2 (n = 14) to 2.33 .+-. 0.67 ng/cm2 .cntdot. min at 14 dyne/cm2 (n = 10). The time integral of production of total production did not significantly change with shear stress, at least for shear stresses > 0.9 dyne/cm2. Once stressed, cell monolayers produced additional prostacyclin in response to stimulation by sodium arachidonate or the calcium ionophore A23187 [calcinomycin], but not to repeat mechanical stimulation. Endothelial cells produce bursts of prostacyclin in response to suddenly imposed arterial-like shear stress and the peak rate, but not the time integral, of this production increases with shear stress.