Transporters and Ion-Channels play a major role in cell membranes. In the last years they have come more and more into the focus of pharmacological research. Transport proteins of the small intestine, kidney and liver are not only important for transport of endogenous compounds, but also for that of xenobiotics, toxins and drugs. In particular, they are responsible for reabsorption and excretion of anionic and cationic pharmaceuticals.

We established expression and preparation of physiological active transporters in membranes of mammalian and insect cells. Here we present rapid and easy to handle assays for the analysis of electrogenic transporters in membranes fractions, using the novel SURFE2R (Surface Electrogenic Event Reader) technology. This cell free, chip based measurement, allows efficient drug screening without using fluorescent or radioactive markers. Km-values for different substrates and IC50 -values for specific inhibitors were determined. In particular, we are capable to compare the substrate specificity for different isoforms of the transporters.