[Effects of osthole on the isolated guinea-pig ileum and taeniae coli]

Effects of osthole (Ost) and verapamil (Ver) were investigated in the isolated guinea-pig ileum and taeniae coli. In the isolated guinea-pig ileum or taeniae coli, Ost and Ver were both found to inhibit the contractions induced by acetylcholine (ACh), histamine (His) and KCl in a dose-dependent manner; and noncompetitively antagonize the CaCl2 cumulative dose-response curves, with pD2 values of 4.41 +/- 0.15 and 7.0 +/- 0.2, respectively. Ost at dose of 100 mumol/L and Ver at 1 mumol/L inhibited CaCl2 0.2 mmol/L induced the contractions of the isolated guinea-pig taeniae coli, and the contractions can be abolished by adding CaCl2 2 mmol/L in Ca(2+)-free medium; both of them showed pronounced inhibitions on intracellular calcium-dependent contractions induced by ACh, but showing no effects on the extracellular calcium-dependent contractions. These results indicate that Ost has calcium antagonistic effect and is similar to Ver in mechanism.