Nitric oxide exposure and sulfhydryl modulation alter image-arginine transport in cultured pulmonary artery endothelial cells

The effect of nitric oxide (NO) exposure and sulfhydryl-reactive chemicals on L-arginine transport in pulmonary artery endothelial cells was evaluated. Exposure of pulmonary artery endothelial cells to 7.5 ppm (0.4μM) NO for 4 h resulted in a significant (p < 0.05) reduction of Na+-dependent but not Na+-independent L-arginine transport. More prolonged exposure for 12–24 h reduced both Na+-dependent and Na+-independent transport of L-arginine with maximal loss of transport after 18 h of exposure (p < 0.02 for both). Similarly, incubation of cells in the presence of 50–200μM S-nitroso-acetyl-penicillamine (SNAP) (but not 500 AM each of nitrate or nitrite) for 2 h also reduced both the Na+-dependent and Na+-independent transport of L-arginine (p < 0.05 for all concentrations). The SNAP-induced reduction of image transport was blocked by the NO scavenger oxyhemoglobin. When cell monolayers were exposed to varying concentrations of the sulfhydryl reactive chemicals image (NEM) and acrolein, a dose-dependent reduction of image transport by both Na+-dependent and Na+-independent processes was observed. Na+-dependent L-arginine transport was more susceptible to inhibition by exposure to NO and to sulfhydryl reactive chemicals. Incubation of cells with 0.5 mM of the thiol-containing agent image prior to and during NEM or acrolein exposure blocked NEM and acrolein-induced reduction of image transport by both Na+-dependent and Na+-independent processes. Similarly, NO-induced reductions of Na+-dependent and Na+-independent image transport were reversed to control levels 24 h after termination of NO exposure. Treatment with the disulfide reducing agent dithiothreitol after exposure to NO resulted in partial reversal of the decreases in image transport. These results demonstrate that exposure to exogenous NO is responsible for reversible reductions of plasma membrane-dependent image transport mediated by both the Na+-dependent (system B0,+) and the Na+-independent (system y+) transport processes. Modulation of the sulfhydryl status of plasma membrane proteins involved in L-arginine transport, such as image transporters and/or Na+/K+-ATPase, may be responsible, at least in part, for reductions in overall image transport in pulmonary artery endothelial cells.