NITRIC-OXIDE PRODUCTION BY CULTURED HUMAN AORTIC SMOOTH-MUSCLE CELLS - STIMULATION BY FLUID-FLOW

This study demonstrated that exposure of cultured human aortic smooth muscle cells (SMC) to fluid flow resulted in nitric oxide (NO) product ion, monitored by nitrite and guanosine 3',5'-cyclic monophosphate pro duction. A rapid burst in nitrite production rate was followed by a mo re gradual increase throughout the period of flow exposure. Neither th e initial burst nor the prolonged nitrite production was dependent on the level of shear stress in the range of 1.1-25 dyn/cm(2). Repeated e xposure to shear stress after a SO-min static period restimulated nitr ate production similar to the initial burst. Ca2+-calmodulin antagonis ts blocked the initial burst in nitrite release. An inhibitor of nitri c oxide synthase (NOS) blocked nitrite production, indicating that cha nges in nitrite reflect NO production Treatment with dexamethasone or cycloheximide had no effect on nitrite production, Monoclonal antibodi es directed against the inducible and endothelial NOS isoforms showed no immunoreactivity on Western blots, whereas monoclonal antibodies di rected against the neuronal NOS gave specific products. These findings suggest that human aortic SMC express a constitutive neuronal NOS iso form, the enzymatic activity of which is modulated by flow.