spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by FRESSER, F.
Right arrow Articles by MAIR, N.
Right arrow Search for Related Content
PubMed
Right arrow Articles by FRESSER, F.
Right arrow Articles by MAIR, N.
Journal of Experimental Biology 157,227-241 (1991)
Published by Company of Biologists 1991

Intra- and Extracellular Use and Evaluation of Ammonium-Selective Microelectrodes

F. FRESSER 1, H. MOSER 1, and N. MAIR 1

1 Institut für Zoologie Technikerstraße 25, A 6020 Innsbruck, Austria

To whom correspondense and requests should be addressed.

1. An NH4+-selective membrane for microelectrodes (NH4ISMs) was tested under ‘biological conditions’ in normal Astacus saline (NAS), two simulated intracellular salines (SIS) and the sensory neurone of the crayfish stretch receptor.

2. The effects of several physiological variables on intracellular NH4+ measurements were tested in vitro. Changes in the background K+ and Na+ concentrations, the ratio K+/Na+, pH, ionic strength, osmotic pressure and volume were examined.

3. Phenomena specific for NH4ISMs, such as a positive potential shift, an undershoot and a difference between pre- and postcalibration curves are described and discussed. We propose to consider the values of intracellular NH4+ concentration as apparent.

4. The detection limit of the NH4ISM is closely related to background K+ concentration. It is in the region of 0.1 mmoll-1 NH4+ in NAS (at 5.4mmol l-1 K+) and about 5mmoll-1 in SIS (at 194mmol l-1 K+).

5. When comparing levels of intracellular NH4+, either measured directly by NH4ISM or calculated, according to Boron and de Weer (J. gen. Physiol. 67, 91-112), from simultaneously recorded pHi, we found that [NH4+]i obtained by direct measurement differed quantitatively from that of the Boron and de Weer model, but that some of the qualitative and temporal aspects of the model agreed with our results. The quantitative difference in [NH4+]i determined by the two methods cannot be attributed to temporal and/or quantitative limitations of the NH4ISM.

Key words: ammonium-selective microelectrodes, ammonium, intracellular pH regulation, stretch receptor, crayfish, Astacus astacus

Accepted on January 28, 1991






© The Company of Biologists Ltd 1991