THE EFFECT OF MEMBRANE-SURFACE POTENTIAL ON THE PERMEABILITY OF ANIONIC COMPOUNDS ACROSS THE APICAL MEMBRANE IN HUMAN INTESTINAL EPITHELIAL(CACO-2) CELLS

The effect of membrane surface potential of the apical side on the int racellular uptake of ionic compounds was investigated using the human colon adenocarcinoma cell line (Caco-2). The transepithelial transport of indolepropionic acid and tryptamine was consistent with the uptake behavior shown by rat intestinal brush-border membrane (BBM) vesicles . Imipramine, which diminished the negative charge of the membrane sur face (for both Caco-2 and BBM), acted to increase the uptake of the an ionic compounds, indolepropionic acid and ceftibuten, and to decrease that of tryptamine (cationic compound) by both the Caco-2 monolayer an d the intestinal BBM vesicles at a pH of 7.5. These results suggest th at the effects of membrane surface potential on the permeability of io nic compounds were detectable on the Caco-2 cell line as well as the B BM vesicles. On the other hand, the inhibition of H+-linked transport and the stimulation of the surface charge-regulated uptake of ceftibut en have occurred simultaneously on the Caco-2 cell line in the presenc e of imipramine. It seems that the membrane surface charge (negative) plays an important role in the transport process of ionic compounds ac ross the intestinal epithelium.