Department of Anesthesia Faculty Articles
PubMed Identifier
6742123
Association Between HCO3(-) Absorption and K+ Uptake by Amphiuma Jejunum: Relations Among HCO3(-) Absorption, Luminal K+, and Intracellular K+ Activity
Publication Title
American Journal of Physiology
Publisher
American Physiological Society
ISSN
0002-9513
Publication Date
June 1984
Abstract
Titration techniques and K+- sensitive microelectrodes have been used to investigate the relations among HCO3(-) absorption, luminal K+, and intracellular K+ activity in in vitro Amphiuma jejunum. The HCO3(-) absorptive flux (JHCO3(-] measured by pH-stat under short circuit was reduced by removal of K+ from the medium but not by replacement of Na+ with choline. JHCO3(-) exhibited a seasonal variation when K+ was absent from the media and was increased to a maximum when K+ equaled 5 mM. Addition of K+ to a K+-free luminal medium stimulated JHCO3(-) much more than addition to the serosal medium. Acetazolamide (10(-4) M) blocked K+-stimulated HCO3(-) absorption while benzolamide reduced the short-circuit current associated with HCO3(-) absorption much more rapidly when added to the mucosal bathing medium. Intracellular K+ activity (aik) and mucosal membrane potential (psi m) of jejunal villus cells were measured with double-barreled microelectrodes. When bathed bilaterally with HCO3(-)-containing media, K+ was actively accumulated for many hours (aik = 58.5 mM) but in the presence of ouabain fell to equilibrium (16 mM) after 2 h. In contrast, when HCO3(-) absorption was induced by removal of serosal HCO3(-), aik was elevated to 83.6 mM and, after 4-h exposure to ouabain cell K+, remained far above electrochemical equilibrium at 33 mM. Tissues bathed in Na+-free (Tris) media containing ouabain retained cell K+ after 4 h at even higher levels (46 mM). Cell K+ activity was reduced by removal of K+ from either the mucosal or serosal medium. Acetazolamide reduced aik over 2 h in Na+-free media from 66 to 42 mM. The decline in aik was associated with a concomitant decline in the HCO3(-) absorptive current. It is concluded that K+ is actively accumulated across both luminal and serosal membranes of the jejunal absorptive cell and that the luminal uptake mechanism is linked to HCO3(-) absorption or an equivalent process.
DOI
https://doi.org/10.1152/ajpgi.1984.246.6.g732
Volume
246
Issue
6
First Page
G732
Last Page
G744
Funding Information
17361/PHS HHS/United States
PubMed ID
6742123
Disciplines
Anesthesiology
NSUWorks Citation
Imon, Michael A. and White, John F., "Association Between HCO3(-) Absorption and K+ Uptake by Amphiuma Jejunum: Relations Among HCO3(-) Absorption, Luminal K+, and Intracellular K+ Activity" (1984). Department of Anesthesia Faculty Articles. 2.
https://nsuworks.nova.edu/hpd_anes_facarticles/2