The main aim of this diploma thesis was to study the role of aldehyde dehydrogenase II (ALDH2) in glycerol trinitrate (GTN) bioactivation. Therefore, humane and porcine smooth muscle cells (HUVSMC and PASMC, respectively) were cultivated in the appropriate media up to a confluency of 80-90 %.To investigate this issue, protein expression of ALDH2 and soluble guanylate cyclase (sGC) was measured by Western blot analysis and formation of cGMP in cells was quantified by radioimmunoassay. Results showed that in both cell types ALDH2 as well as sGC was expressed at least up to passage 10. However, stimulation of HUVSMC with various concentrations of GTN and of the classical NO-donor diethylammonium(Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA/NO) did not result in significantly increased cGMP formation. By contrast, in PASMC a massive increase in cGMP production was observed upon stimulation with DEA/NO.Furthermore, the effect of the NO- and heme-independent sGC-activator cinaciguat on cGMP formation was tested in HUVSMC. Again, no significant increase of cGMP formation was observed under these conditions.Possible explanations for these results are fragmentation of sGC at its -subunit or lack of cellular substrate guanosine triphosphate. Cultivation of cells in a specially developed differentiation medium will be tested in future experiments to yield expression of a functionally active sGC in HUVSMC.