Gonzalez M J, Aguilar M V, Martinez Para M C
Dpto Nutricion y Bromatologia, Facultad de Farmacia, Universidad de Alcala de Henares, Madrid, Spain.
Vet Hum Toxicol. 1995 Apr;37(2):131-6.
The absorption of inorganic pentavalent arsenic (As) by the rat small intestine was investigated using 2 different procedures: In vivo determination of overall extent of gastrointestinal absorption; and an intestinal perfusion technique. The aim was to determine the effect of concentration and the interaction with phosphate and dichromate anions on gastrointestinal absorption of As to understand the mechanism of As absorption at intestinal level. The results indicate there is a direct relationship, although not proportional, between the received dose and the absorbed amount of As. Intestinal absorption of As appears carried out by a saturable transport process. The phosphate produces a pronounced decrease in the intestinal absorption of As due to the fact that phosphate and As can share the same transport mechanism which is an active secondary carrier-mediated system depending on Na+ and H+ gradient. Addition of dichromate to perfusion buffers significantly (p > 0.05) increased As absorption. Several hypothesis may explain this fact: Dichromate produces pH modifications at the intracellular level, providing an adequate H(+)-gradient for As absorption; dichromate exerts a caustic effect, which damages the intestinal wall at the microvilli level. This allows free diffusion of As through the resulting openings.
采用两种不同方法研究了大鼠小肠对无机五价砷（As）的吸收：胃肠道吸收总体程度的体内测定；以及肠灌注技术。目的是确定浓度以及与磷酸根和重铬酸根阴离子的相互作用对砷胃肠道吸收的影响，以了解肠道水平砷吸收的机制。结果表明，接受剂量与砷吸收量之间存在直接关系，尽管并非成正比。砷的肠道吸收似乎是通过可饱和转运过程进行的。磷酸盐使砷的肠道吸收显著降低，这是因为磷酸盐和砷可共享相同的转运机制，该机制是一种依赖于Na+和H+梯度的主动继发性载体介导系统。向灌注缓冲液中添加重铬酸盐显著（p>0.05）增加了砷的吸收。有几种假设可以解释这一现象：重铬酸盐在细胞内水平产生pH变化，为砷吸收提供足够的H(+)-梯度；重铬酸盐发挥腐蚀作用，在微绒毛水平损伤肠壁。这使得砷能够通过形成的开口自由扩散。
