8-(N,N-DIETHYLAMINO)-n-OCTYL-3,4,5-TRIMETHOXYBENZOATE(TMB-8) REDUCED THE ELEVATION OF Ca²⁺i INDUCED BY BHQ, NE AND KCl IN CULTURED SINGLE SMOOTH MUSCLE CELLS OF THE CALF BASILAR ARTERY

The effect of 8-(N,N-diethylamino)-n-octyl-3,4,5-trimethoxybenzoate (TMB-8) on the elevation of Ca²⁺i induced by 2,5-di(tert-butyl)-1,4-benzohydroquinone (BHQ), norepinephrine (NE), KCl in cultured single smooth muscle cells of the calf basilar artery was studied by a system of measurement of AR-CM-MIC, using Fura-2/AM as a fluoresent indicator. In the presence of extracellular Ca²⁺ 1.3 mmol·L^-1, the resting Ca²⁺i was not changed by TMB-8 (10, 30 and 100 μmol·L^-1), but the elevation of Ca²⁺i induced by BHQ, NE and KCl were reduced by TMB-8 (30 μmol·L^-1) significantly. In Ca²⁺ free Hank′s solution containing EGTA 0.1 mmol·L^-1, the resting Ca²⁺i was markedly reduced by TMB-8 (10,30 and 100 μmol·L^-1), and the increase of Ca²⁺i evoked by BHQ and NE was blocked completely by TMB-8 (30 μmol·L^-1). The result suggested that TMB-8 inhibited the Ca²⁺ release from intracellular stores or increased the up-take of Ca²⁺ into sarcoplasmic reticulum and the inhibition of Ca²⁺-influx from extracellular site may be an indirect machanism.