The Effects of Five Alkaloids from Bulbus Fritillariae on the Concentration of cAMP in HEK Cells Transfected with Muscarinic M2 Receptor Plasmid

The aim of this study was to investigate the effects of five alkaloids, namely verticine, verticinone, imperialine, imperialine-3β-D-glucoside, and puqietinone, purified from Bulbus Fritillariae and used as an antitussive drug in traditional Chinese medicine, on their antimuscarinic M2 function and the cAMP level of HEK cells transfected with muscarinic M2 receptor plasmid. By transfecting the HEK cells with the method of calcium phosphate co-precipitation and screening with G418, the cells stably expressing M2 receptor were identified. The expression of M2 receptor in HEK cells was confirmed by both RT-PCR and western blot. The cAMP level in the treated cells was analyzed with RIA method (125I-cAMP KIT). And the results suggested that the five alkaloids could significantly elevate the cAMP concentration in the HEK cells transfected with muscarinic M2 receptor plasmid (p < 0.01).