González M J, Aguilar M V, Martínez M C
Departamento de Nutrición y Bromatología, Facultad de Farmacia, Universidad de Alcalá de Henares, Madrid, Spain.
J Trace Elem Med Biol. 1997 Dec;11(4):239-47. doi: 10.1016/S0946-672X(97)80019-3.
The main purpose of this research was to study the effects of water movement on arsenic absorption. In order to appreciate and measure the interaction between these two variables we investigated the perfusion of isotonic and hypotonic buffers (containing 3.2 microgram/ml As2 O5 into rat small intestines. The As (V) depended on osmolarity sensitive. This implied the presence of a saturable uptake kinetic mechanism and suggested the participation of some kind of carrier-mediated transport system. An increase in arsenate absorption and its accumulation in organs was detected in the presence of an Na+ gradient. The same technique, combining isotonic buffers with different pH values and buffers containing valinomycin, was used in order to study the effects of intraluminal pH on membrane potential. A significant decrease in arsenic levels and As(V) absorption in organs was detected as a result of an increase in the pH. This influence of pH on the As(V) absorption mechanism indicated dependence on a proton (H+) gradient. An inside negative potassium potential induced by valinomycin increased significantly the uptake of arsenate, suggesting an electrogenic transport of arsenate. In conclusion, the As(V) might be absorbed from the small intestine through a carrier-mediated mechanism, which would depend on the Na+(-) and H+(-)gradients and the membrane potential differential from both sides of the intestinal epithelial cells.
本研究的主要目的是研究水的流动对砷吸收的影响。为了理解和测量这两个变量之间的相互作用，我们研究了将等渗和低渗缓冲液（含3.2微克/毫升As2O5）灌注到大鼠小肠中的情况。五价砷（As(V)）对渗透压敏感。这意味着存在一种可饱和的摄取动力学机制，并表明某种载体介导的转运系统参与其中。在存在钠离子梯度的情况下，检测到砷酸盐吸收增加及其在器官中的积累。为了研究肠腔内pH值对膜电位的影响，采用了相同的技术，即将不同pH值的等渗缓冲液与含有缬氨霉素的缓冲液相结合。由于pH值升高，检测到器官中的砷水平和五价砷吸收显著降低。pH值对五价砷吸收机制的这种影响表明其依赖于质子（H+）梯度。缬氨霉素诱导的内向负钾电位显著增加了砷酸盐的摄取，表明砷酸盐的电转运。总之，五价砷可能通过载体介导的机制从小肠吸收，这取决于钠离子（-）和质子（-）梯度以及肠上皮细胞两侧的膜电位差。
