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.
Department of Medicine, University of Illinois, Chicago.
J L
JL
Goldstein
B G
BG
Fogelson
J C
JC
Snow
L N
LN
Schmidt
H
H
Mozwecz
T J
TJ
Layden
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