P-CHLOROBENZYLTETRAHYDROBERBERINE INHIBITS VASCULAR SMOOTH-MUSCLE CONTRACTIONS CAUSED BY CA2+1

AIM: To investigate influences of p-chlorobenzyltetrahydroberberine (C PU-86017) and levothyroxin (Lev) on vascular smooth muscle (VSM) contr actions by intracellular Ca2+ release and calcium entry. METHODS: Thre e kinds of contractions of rat thoracic aortic rings were used to comp are suppression by CPU-86017, bepridil ( Rep), verapamil ( Ver), and n imodipine (Nim) in euthyroid- and Lev-induced hyperthyroidism rats. RE SULTS: The IC50 Of CPU-86017 on KCl-induced contractions of euthyroid and hyperthyroid VSM were 80 (36 - 179) and 121 (62 - 236) mu mol . L- 1, respectively. The potency of CPU-86017 was approximate to 1/10 of B ep and 1/100 of Ver and Nim. Suppressions of Ver and Nim on hyperthyro id VSM in Ca2+-free solution were greatly attenuated by -86% and -95%, respectively. Slight or no change in activity of CPU-86017 and Bep wa s found. Contractions on adding Ca2+ into Ca2+-free medium were suppre ssed 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 bo th.