This diploma thesis was aimed at answering the following questions: which Gq protein-coupled receptors are expressed in isolated smooth muscle cells of porcine aorta (PASMC), porcine trachea (PTSMC) and bovine coronary arteries (BCASMC), and, do they change their properties upon prolonged culture of the cells. To answer these questions, the smooth muscle cells were isolated from the respective tissues, loaded with the fluorescence dye fura-2 / AM and suspended in either Ca2+-containing or in Ca2+ -free TRIS buffer. Subsequently, the intracellular Ca2+ concentrations ([Ca2+]) was determined by fluorescence analysis. The results showed that PASMC and PTSMC suspended in Ca2+ free TRIS-buffer responded to addition of Ca2+ with a pronounced increase in [Ca2+]i, suggesting a high Ca2+ permeability. In accordance with this conclusion, cells suspended in Ca2+ containing TRIS buffer had very high basal Ca2+ levels, independent of the passage. In contrast to the porcine cells, BCASMC exhibited rather low basal [Ca2+] levels, but the Ca2+ permeability of the membrane increased with increasing of the passage.In a further experimental approach, the cells were tested for receptor expression by adding various agonists. The results showed that all cells markedly responded to bradykinin throughout all passages, demonstrating robust expression of the B2-receptor. Similarly, 5-HT2 receptors were found in PASMC even after long-term culture. In PTSMC, angiotensin II enhanced Ca2+ levels in the low and middle passage, confirming the expression of the AT1 receptor subtype. In contrast to PASMC and PTSMC, BCASMC also responded to histamine and endothelin-1, but the effect was lost in high passages. Summarized, these data demonstrate that smooth muscle cells isolated from porcine aorta, porcine trachea and bovine coronary arteries express a variety of Gq-protein coupled receptors but the expression profile may change with increasing passage.