ISSN:
1432-1424
Keywords:
Na+-K+-ATPase
;
Electrophysiology
;
K+ channel
;
Tetraethylammonium
;
Conductance regulation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Using the two-microelectrode voltage clamp technique in Xenopus laevis oocytes, we estimated Na+-K+-ATPase activity from the dihydroouabain-sensitive current (I DHO) in the presence of increasing concentrations of tetraethylammonium (TEA+; 0, 5, 10, 20, 40 mm), a well-known blocker of K+ channels. The effects of TEA+ on the total oocyte currents could be separated into two distinct parts: generation of a nonsaturating inward current increasing with negative membrane potentials (V M) and a saturable inhibitory component affecting an outward current easily detectable at positive V M. The nonsaturating component appears to be a barium-sensitive electrodiffusion of TEA+ which can be described by the Goldman-Hodgkin-Katz equation, while the saturating component is consistent with the expected blocking effect of TEA+ on K+ channels. Interestingly, this latter component disappears when the Na+-K+-ATPase is inhibited by 10 μm DHO. Conversely, TEA+ inhibits a component of I DHO with a k d of 25±4 mm at +50 mV. As the TEA+-sensitive current present in I DHO reversed at −75 mV, we hypothesized that it could come from an inhibition of K+ channels whose activity varies in parallel with the Na+-K+-ATPase activity. Supporting this hypothesis, the inward portion of this TEA+-sensitive current can be completely abolished by the addition of 1 mm Ba2+ to the bath. This study suggests that, in X. laevis oocytes, a close link exists between the Na-K-ATPase activity and TEA+-sensitive K+ currents and indicates that, in the absence of effective K+ channel inhibitors, I DHO does not exclusively represent the Na+-K+-ATPase-generated current.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00232521
Permalink
