Measurements of electrical potentials and ion fluxes on single renal tubules. Circulation 21 : 879

Experimental technics are described which permit the measurements of stable electrical potential differences across the cell membrane of single renal tubule cells and across single tubules. The inside of the tubule lumen is normally found to be electrically nega-tive to the outside, while the cell interior is found to be negative to both the peritubular fluid and the tubule lumen. Such electrical measurements, in conjunction with known concentration gradients and flux measurements of various ions across single renal tubules, permit some deductions to be made on the driving forces involved in the move-ment of various ion species across the luminal and peritubular cell membrane of renal tubule cells. RENAL function studies have indicated that among biologic membranes involved in the transport of electrolytes, the renal tubules are exceedingly active in the net trans-fer of most ion species. However, in spite of the establishment of considerable coneentra-tion gradients across various tubular segments and the likelihood of different transfer rates of charged particles from the lumen to the peritubular fluid, factors favoring the crea-tion of electrical potential differences, renal tubular structures have received relatively little attention as far as electrical phenomena are concerned. Also, little is known regarding the magnitude and the kinetics of bidirectional ion fluxes across renal tubules, although site and steepness of various ionic concentration gradients have been fairly well outlined by micropuncture studies on individual nephrons. Some of these problems have recently beeni studied by a combination of microelectrode technics and the perfusion of single renal tubules with solutions of known compositio