Schäfer S G, Forth W
Arch Toxicol. 1987 Apr;59(6):413-20. doi: 10.1007/BF00316207.
Unidirectional Tl+-fluxes across the isolated mucosa of rat descending colon were measured under short circuit (SCC) or voltage clamp conditions (VCC). Under SCC a serosal-to-mucosal net flux (Jnet = -0.22 nmol X cm-2 X h-1) was observed that agrees with the voltage-independent component measured under VCC. At 7 degrees C the secretory net flux was abolished. In controls both unidirectional fluxes were unsaturable between 0.1 and 500 mumol/l thallium (I). After furosemide or withdrawal of Cl- or Na+ Jnet was abolished. Ouabain decreased serosal-to-mucosal Tl+ flux and an energy-dependent absorptive net flux of Tl+ was observed, characterized by a rather low Km (10.2 mumol/l), Vmax (3.8 nmol X cm-2 X h-1) and apparent activation energies (delta E = 10.7 kcal X mol-1) typically for enzyme catalaysed reactions or narrow channel interactions. The data suggest that in the mucosa of rat descending colon Tl+ ions share, at least in part, the same transport systems at K+.
在短路（SCC）或电压钳制条件（VCC）下，测量了铊离子（Tl⁺）跨大鼠降结肠离体黏膜的单向通量。在SCC条件下，观察到浆膜到黏膜的净通量（Jnet = -0.22 nmol·cm⁻²·h⁻¹），这与在VCC条件下测量的电压非依赖性成分一致。在7℃时，分泌性净通量消失。在对照中，在0.1至500 μmol/L铊（I）之间，两个单向通量均不饱和。在使用速尿或去除氯离子或钠离子后，Jnet消失。哇巴因降低了浆膜到黏膜的Tl⁺通量，并观察到Tl⁺的能量依赖性吸收净通量，其特征在于Km相当低（10.2 μmol/L）、Vmax（3.8 nmol·cm⁻²·h⁻¹）以及表观活化能（ΔE = 10.7 kcal·mol⁻¹），这通常是酶催化反应或狭窄通道相互作用的特征。数据表明，在大鼠降结肠黏膜中，Tl⁺离子至少部分地与钾离子共享相同的转运系统。
