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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/3659

Title: MEASUREMENT OF INTRACELLULAR AND LUMINAL K+ CONCENTRATIONS IN A MALPIGHIAN TUBULE (FORMICA) - ESTIMATE OF BASAL AND LUMINAL ELECTROCHEMICAL K+ GRADIENTS
Authors: LEYSSENS, Anne
VAN KERKHOVE, Emmy
ZHANG, SL
WELTENS, R
STEELS, Paul
Issue Date: 1993
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Citation: JOURNAL OF INSECT PHYSIOLOGY, 39(11). p. 945-958
Abstract: Cellular and luminal K+ concentrations were measured in different bath K+ concentrations using double-barrelled K+-selective electrodes. The electrochemical gradient for K+ across the basal and the apical cell membrane was estimated. The experiments were performed in two Cl- concentrations. In control Ringer (41 mM K+ and 57 mM Cl-) cell K+ was 82 mM and luminal K+ was 119 mM. On lowering bath K+ to 4 mM or increasing it to 90 mM cell K+ and to a lesser extent luminal K+ followed: cell K+ changed to 29 and 90 mM and luminal K+ to 106 and 132 mM, respectively. In a 143 mM Cl- Ringer solution cellular and luminal K+ concentration showed a similar change with the basal K+ concentration. The basal membrane potential difference was almost equal to the equilibrium potential for K+ in all bath K+ and Cl- concentrations tested and the estimated electrochemical gradient for K+ across the basal membrane was very small (inward, zero, or even outward in low bath K+). It tended to become more inward as the bath K+ increased. The methods for estimating such a small gradient and the idea of passive K+ uptake through K+ channels across this barrier was critically evaluated. The large transepithelial electrochemical gradient against which K+ was transported was primarily situated in the apical membrane. This gradient decreased as the bath K+ was elevated (and fluid secretion accelerated): an increase in the bath K+ reduced both the electrical and concentration step to be overcome for K+ secretion across the apical membrane. A double role for the bath K+ in the regulation of K+ secretion is proposed.
Notes: LIMBURGS UNIV CENTRUM,PHYSIOL LAB,B-3590 DIEPENBEEK,BELGIUM.
URI: http://hdl.handle.net/1942/3659
DOI: 10.1016/0022-1910(93)90004-B
ISI #: A1993MK10700004
ISSN: 0022-1910
Type: Journal Contribution
Appears in Collections: Research publications

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