Effects of cocaine on nitric oxide production in bovine coronary artery endothelial cells.

Cocaine decreases coronary artery endothelial-dependent vasorelaxation. To explore the potential mechanisms, the present study examined the effect of cocaine on nitric oxide release in bovine coronary artery endothelial cells (BCAECs). In the absence of cocaine, basal nitric oxide release from BCAECs continued to accumulate in the medium over the period from 6 to 72 h. Cocaine significantly decreased nitric oxide release at each time point of the study. At 48-h treatment, cocaine (3-30 muM) produced a concentration-dependent decrease in nitric oxide release in BCAECs. In accordance with its inhibition of nitric oxide release, cocaine decreased endothelial nitric-oxide synthase (eNOS) protein levels in BCAECs in a concentration-dependent manner. In addition to the prolonged effect, cocaine pretreatment for 1 h significantly decreased basal and ATP-induced nitric oxide release in BCAECs. Whereas acute cocaine treatment did not affect basal levels of free intracellular calcium concentrations in BCAECs, it significantly decreased the ATP-induced elevation of intracellular calcium and increased its time lag to reach the peak. A quantitative approach by immunofluorescence microscopy revealed that cocaine significantly increased eNOS localized at the cell membrane in BCAECs. Collectively, the results suggest that cocaine inhibits nitric oxide release in BCAECs by decreasing intracellular calcium mobilization, increasing the inactive state of eNOS, and decreasing eNOS protein levels.