Short-circuit current measurements in proximal tubule of Necturus kidney

Abstract

A modified short-circuit method, which requires only one pair of electrodes, was applied to the proximal tubule of the Necturus kidney for determination of the short-circuit current as a measure of active ion transport across the tubular wall. The indifferent electrode was placed on the surface of the exposed kidney and the tubular lumen was punctured with a microelectrode. After injection of oil into the glomerulus of the same nephron, a marked increase in electrical resistance between the electrodes during oil passage at the puncture site indicated the proper position of the electrode tip in the tubular lumen. The largest area effectively short-circuited (12.5 x 10–4 cm2) was determined by changing the position of two oil droplets between which measurements were made. Thirteen measurements of the short-circuit current in anesthetized normal Necturi averaged 4.8 x 10–6 amp/cm2, which corresponds to an active monovalent ion transport of 4.6 x 10–11 Eq/cm2 x sec.