Untersuchungen über die Ausspritzmethode zur Lokalisation der Mikroelektrodenspitze bei Potentialmessungen am proximalen Konvolut der Rattenniere

✍ Scribed by E. Frömter; T. Wick; U. Hegel

• Publisher: Springer
• Year: 1967
• Tongue: English
• Weight: 747 KB
• Volume: 294
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00363112

✦ Synopsis

In measurements of transtubular potential differences of the rat kidney, reported previously, the electrode tip could be localized by ejection of electrode fluid under microscopic observation. In the proximal tubule it was found in contrast to the distal tubule that all potential differences disappeared irreversibly upon fluid ejection. The present study is concerned with the mechanism underlying this effect.

The localization of the puncturing electrode was controlled by a coupling pulse technique. Current pulses were injected into the tubular lumen through a first electrode, and the same tubule was punctured subsequently with a second electrode which measured the potential difference. It was found that in most impalements the puncturing electrode would stop within the tubular wall, although from microscopic inspection it appeared to have reached the tubular lumen. Furthermore, when fluid was ejected from the electrode tip, the electrode abruptly penetrated into the tubular lumen. Simultaneously the potential difference recorded hitherto disappeared. This coincidence suggests that the breakdown of the potential difference merely corresponds to the potential step between cellular compartment and tubular lumen and that it is not caused by a transtubular leak.

Conclusive evidence against the development of leaks during fluid ejection was derived from microperfusion experiments. During perfusion of the tubular lumen with choline chloride solution proximal tubules develop a transtubular potential difference significantly different from zero (up to 30 mV, lumen positive). Whether the electrode entered the tubular lumen during the impalement immediately, or whether the penetration was only accomplished by fluid ejection, did not affect the magnitude of the positive potential differences recorded. Hence these experiments constitute proof that the method of fluid ejection permits reliable measurements of transtubular potential differences in the proximal tubule. They confirm our finding that under normal free flow conditions no transtubular potential difference exists across the proximal tubular epithelium of the rat kidney.

In einer vorangehenden Mitteflung [2] haben wir fiber Untersnehungen der elektrischen Potenti~ldifferenzen an eorticalen Tubuli der Ratte~lniere berichte~. Dabei h~te sich gezeigt, da~ am proxim~len Tubulus * ]~Iit Unterstfitzung dnreh die Deutsche Forsehungsgemeinschaft.