123388-25-0

Ca ²⁺ channel

Semotiadil in a concentration of 1 μM produces an inhibition of 12.4±9.7% and in a concentration of 10 μM an inhibition of 25±11.0%. Effects of Semotiadil on the voltage-dependent Ca current (ICa) are investigated in dispersed smooth muscle cells of the rabbit portal vein. At a holding potential of -100 mV, Semotiadil (> or =0.1 μM; dissolved in DMSO) inhibits the ICa in a concentration-dependent manner (IC ₅₀ =2.0 μM). At a holding potential of -80 mV or -60 mV, the concentration-inhibition curve observed in the presence of Semotiadil is shifted to the left compared with that observed at -100 mV; and Semotiadil shifts the voltage-dependent inactivation curve to the left. The curve for the decay of ICa is fitted with two time constants. Semotiadil (<1 μM) reduces the slow but not the fast time constant. The curve for the recovery from ICa inactivation also consisted of two time constants, and Semotiadil (1 microM) prolongs the slow recovery. Semotiadil dissolved in deionized water more potently inhibits ICa than Semotiadil dissolved in DMSO.

Semotiadil fumarate, a novel benzothiazine calcium antagonist, is given alone or in combination with either Enalapril or trichlormethiazide to conscious, spontaneously hypertensive, rats daily for 2 weeks. When given alone, the antihypertensive effects of Semotiadil (10 mg/kg, p.o.) and Enalapril (5 mg/kg, p.o.) first became apparent after the 3rd dose and thereafter the effects appeared to develop daily although this effect had waned by the time of the next dose. These results indicate that combined daily dosing of Semotiadil, especially with Enalapril, each at relatively low doses may be able to control hypertension in a continuous manner.