Rabbit esophageal cells possess K+ channels: effect of hyposmotic stress on channel activity.
BACKGROUND
In many cell types, basolateral K+ channels are important in maintaining transepithelial Na+ absorption and regulatory volume decrease (RVD) after hyposmolar stress. However, in the esophagus the effect of K+ transport in maintaining baseline short-circuit current (SCC) (Na+ absorption) and RVD is unknown.


METHODS
Ussing chambers were used to evaluate changes in SCC of rabbit esophageal mucosa in response to serosal Ba2+ (4 mmol/L), quinine (1 mmol/L), and increasing serosal [K+]. To determine whether K+ channel(s) are activated in RVD, changes in SCC in response to serosal hyposmolarity (156 mOsm) were assessed in the presence or absence of serosal quinine.


RESULTS
Serosal Ba2+, quinine, or increased serosal [K+] caused a decline in baseline SCC. Serosal hyposmolarity caused an increase in SCC that was not blocked by mucosal application of amiloride (10(-4) mmol/L). In contrast, serosal quinine completely blocked the hyposmolar-induced increase in SCC.


CONCLUSIONS
These studies suggest that rabbit esophageal cells possess Ba(2+)- and quinine-sensitive basolateral K+ channel(s) that are active under baseline conditions. Potassium conductance(s) also appear to be activated by external serosal hyposmolarity and may be involved in the process of RVD.
Goldstein
J L
JL
Department of Medicine, University of Illinois, Chicago.
Fogelson
B G
BG
Snow
J C
JC
Schmidt
L N
LN
Mozwecz
H
H
Layden
T J
TJ
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D004947:Esophagus / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009994:Osmolar Concentration; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011802:Quinidine / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis
D015221:Potassium Channels; D001464:Barium; D000584:Amiloride; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011802:Quinidine