p-Chlorobenzyltetrahydroberberine inhibits vascular smooth muscle contractions caused by Ca2+.
AIM
To investigate influences of p-chlorobenzyltetrahydroberberine (CPU-86017) and levothyroxin (Lev) on vascular smooth muscle (VSM) contractions by intracellular Ca2+ release and calcium entry.


METHODS
Three kinds of contractions of rat thoracic aortic rings were used to compare suppression by CPU-86017, bepridil (Bep), verapamil (Ver), and nimodipine (Nim) in euthyroid- and Lev-induced hyperthyroidism rats.


RESULTS
The IC50 of CPU-86017 on KCl-induced contractions of euthyroid and hyperthyroid VSM were 80 (36-179) and 121 (62-236) mumol.L-1, respectively. The potency of CPU-86017 was approximate to 1/10 of Bep and 1/100 of Ver and Nim. Suppressions of Ver and Nim on hyperthyroid VSM in Ca(2+)-free solution were greatly attenuated by -86% and -95%, respectively. Slight or no change in activity of CPU-86017 and Bep was found. Contractions on adding Ca2+ into Ca(2+)-free medium were suppressed by CPU-86017 and its potencies in euthyroid and hyperthyroid rats were not different.


CONCLUSION
CPU-86017 is more potent to suppress Ca2+ entry than intracellular calcium mobilization and Lev enhances both.