Gerhard Hans Giebisch

our research is concerned with cellular and molecular mechanisms of solute and solvent transport in the kidney. We are studying single renal tubules to obtain information about the mechanisms of transport and the driving forces acting on Na+, Cl-, K+, HCO-, and H+ ions as they traverse the luminal and antiluminal cell membranes of the tubular epithelium. Techniques we are now applying to single tubules include free-flow micropuncture, microperfusion of defined tubular segments, electron microscopy, and several electrophysiological methods: intracellular voltage measurements, cell ion activity measurements, and patchclamping. Cell fluorescence measurements (pH, Ca2+, Na+ etc) are also employed. Specific problems addressed include the mechanism of chloride transport across proximal tubular epithelium: the mechanism of solute-solvent coupling; the relationship between cell Na+ activity, metabolism, and net fluid tranport in single tubule cells; and the relationship amount cell Ca+ activity, cell pH, and cell Na+/K+ pumping during regulation of sodium transport. We have also investigated in detail the cell mechanism of renal potassium transport, including analysis of cloned potassium channels. A new development in our laboratory is the use of several mouse knockout models to study lesion resulting from the selective deletion of the Na-H exchanger (NHE3 and NHE1), the colonic isoform of the K-H exchanger, and the NaCl cotransporter.