Erfahrungen mit der Öltropfenmethode zur Lokalisation der Mikroelektrodenspitze bei transtubulären Potentialmessungen an der Rattenniere

Summary

The reliability of the method for locating the tip of a microelectrode in renal tubules described by Eigler for the Necturus kidney, was investigated in the rat kidney. The method, as originally described, involves the injection of an oil droplet into the tubular lumen upstream from the site of entry of the microelectrode. A reversible increase in electrode resistance during passage of the droplet down the tubule past the microelectrode tip is then taken as proof of intraluminal position of the electrode. In the rat nephron, we have observed, however, that such alterations in electrode resistance can occur even when the electrode is not located within the tubular lumen. Hence, in the present experiments, this method could not be used to distinguish between transtubular and transcellular potential differences. It was therefore concluded that previous measurements of electrical potential differences in rat proximal tubules in which the oil droplet method was used for locating the electrode tip [7–9] cannot be accepted with certainty as transtubular values.