The electrogenic Na‐pump and spontaneous contraction of the hypokalemic rat duodenum

Abstract

1 The effects of the electrogenic Na-pump on spontaneous contraction in the isolated, longitudinal muscle of the duodenum of rats which had been on a potassium-deficient diet for 7 weeks, have been investigated. Intracellular levels of Na+ are increased by this diet. 2 The spontaneous contraction of the duodenal muscle was stopped, transiently, by 0.5 to 120 mM-KC Krebs solution. The period of decrease of tone and amplitude occurring immediately after adding KC was shortened when the external K+ concentration ([K]b) was increased from 0.5 to 120 mM.3 The decrease in tone and amplitude induced by KC was abolished by exposure ofthe tissue to 0 mM [K]b, by exposure to a temperature below 14C, and in the presence of ouabain (3 x 10-5_10-4 M).4 The spontaneous contraction of'Na-rich' duodenum in bathing medium containing 15mM K and following inhibition ofthe electrogenic Na-pump with cooling or ouabain was much the same as in the duodenum from rats fed balanced diets: i.e., increase of contractile tone immediately after adding KV.

Inhibition of the electrogenic Na,K pump and Na,K‐ATPase activity by tetraethylammonium, tetrabutylammonium, and apamin

“…The similarity between the Kf binding site on the Na,K-ATPase and that on the voltage-dependent K+ channel was first noted by Edwards (1982). It is shown by the similar effects of TI+, Rb', Cs+, and NH4f on the two sites (Akaike and Wakita, 1986;Gay and Stanfield, 1978), and by the inhibitory effects of quarternary ammonium cations on both the voltage-dependent K + channels in nerve and those muscle (for review see Stanfield, 1983) and active Na+ and Kf transport in red blood cells (Sachs, 1967;Sachs and Conrad, 1968;Kropp and Sachs, 1977;Ellory et al, 1979;Forbush, 1986). To learn more about the interrelationship between the channel and the pump it seemed of interest to examine the effects of other K+ channel blockers on the Na,K pump.…”