Abstract-Short-term treatment of the endothelium with dihydropyridine calcium antagonists resulted in an increased release in NO that is not due to a modulation of L-type calcium channels, because macrovascular endothelial cells do not express this channel. We investigated whether long-term (48 hours) treatment of porcine endothelial cell cultures with the dihydropyridine calcium antagonist nifedipine resulted in a similar enhanced NO liberation. Regarding to the underlying mechanism, we examined whether (1) nifedipine changed the mRNA and protein levels of the constitutive endothelial NO synthase (NOS) in endothelial cell cultures or (2) nifedipine exerts an NO protective effect via its antioxidative properties, as revealed in a cell culture model and with native endothelium from porcine coronary arteries. ihydropyridine (DHP)-type calcium antagonists are important drugs in the treatment of hypertension and coronary heart disease. They induce their specific pharmacological effects by binding to L-type calcium channels, 1,2 which results in a reduced calcium influx with impaired electromechanical coupling both in vascular smooth muscle cells and in the heart. 3 A few years ago, however, it was observed that removal of the endothelium or blockade of the guanylate cyclase of the vessel wall reduced the efficacy of the DHP-induced vasorelaxation, 4 which indicated an endothelium-responsive cGMP-mediated process as part of the DHP action. Because macrovascular endothelial cells lack voltage-operated L-type calcium channels, 5,6 the DHPs must exert these effects via other mechanisms. In this context, it is worth mentioning that DHPs may also exert antihrombotic 7,8 and antiatherosclerotic 9,10 effects in different experimental and clinical settings, of which the underlying signal transduction remains obscure.With this background, it is tempting to speculate that NO, one of the most prominent endothelium-derived factors, 11,12 which relaxes smooth muscle cells via the cGMP signal cascade, 13 might be involved in these DHP actions. In fact, in various models, evidence has accumulated that DHPs stimulate the endothelial NO release, 14 -19 which may mediate or at least contribute to the abovementioned calcium channel-independent effects.Up to now, however, all of these findings were obtained only after acute exposure to DHPs (lasting minutes to hours). Because patients usually take calcium antagonists for a longer period of time, we investigated whether long-term treatment of endothelial cell cultures with nifedipine may alter the basal endothelial NO release as well as the expression of the constitutive endothelial NO synthase (ecNOS) mRNA and protein. Furthermore, because NO is rapidly deactivated by reactive oxygen species (ROS) 20 and the DHPs may act as scavengers as known from different in vitro models, [21][22][23] we also determined the antioxidative potency of nifedipine in endothelial cell cultures as well as in native cells to reveal a potential NO-protection effect as an underlying mechanism of the increased ...