TMB-8对去甲肾上腺素和BHQ引起新生大鼠单个脑细胞内游离钙增高的影响

应用AR-CM-MIC阳离子测定系统,研究TMB-8对体外新生SD大鼠单个脑细胞内游离钙的抑制作用及其机制。结果表明,在无细胞外钙情况下,静息Ca²⁺]i为79±13nmol·L^-1。TMB-810,30μmol·L^-1能明显降低静息Ca²⁺]i。TMB-8100μmol·L^-1对高钾去极化引起的Ca²⁺]i显著增高无明显影响。在细胞外钙为1.3mmol·L^-1时,去甲肾上腺素诱导的细胞内Ca²⁺]i升高可部分被TMB-8抑制;TMB-8(30μmol·L^-1)对BHQ引起的Ca²⁺]i的升高无明显抑制作用。而当细胞外液Ca²⁺]i为0时,TMB-8几乎完全抑制了去甲肾上腺素和BHQ的作用。提示TMB-8降低脑细胞内游离钙的作用机制是通过促使细胞内钙进入肌浆网以抑制内钙的释放,并通过饱和肌浆网内Ca²⁺间接地阻滞细胞膜钙通道。

EFFECT OF TMB-8 ON THE INCREASE OF INTRACELLULAR FREE CA2+ INDUCED BY NE AND BHQ IN DISSOCIATED SINGLE RAT BRAIN CELL

The inhibitory effect and mechanism of 8-(N, N'-diethylamino) octyl 3, 4, 5-trimethoxybenzoate hydrochloride (TMB-8) on the elevation of single intracellular free Ca2+ concentration (Ca2+]i) induced by High K+, Norepinephrine(NE) and 2, 5-Di(tert-butyl)-1, 4-benzohydroquinone (BHQ) in dissociated single rat brain cells were studied. The changes of Ca2+]i were reflected by the fluorescent indicator, Fura-2/AM, employed. In the absence of extracellular Ca2+, Ca-free Hank's solution, preincubation with TMB-8 (10, 30 mumol.L-1) for 20 min significantly decreased the resting Ca2+]i from 79 +/- 13 nmol.L-1 to 65 +/- 11 and 61 +/- 6 nmol.L-1, respectively. Ca2+]i were markedly increased by NE and BHQ and reduced significantly to control level by TMB-8. On the other hand, when the cells were incubated in Hank's solution containing Ca2+ 1.3 mmol.L-1, TMB-8(30, 100 mumol.L-1) suppressed the increase of Ca2+]i induced by NE (0.0001-0.1 mumol.L-1). TMB-8 showed no significant effect on Ca2+]i elevation induced by KCl and BHQ in Hank's solution containing Ca2+ 1.3 mmol.L-1. These results indicate that TMB-8 reduced Ca2+]i via increase of the sarcoplasmic reticulum (SR) sequestration, which blocked the release of intracellular store from the SR. However, the inhibitory effect of TMB-8 on Ca-influx from extracellular medium seems to be an indirect action from the saturation of SR with calcium.