Studies on ouabain-binding to (Na+ + K+)-ATPase from Malpighian tubules of the locust, Locusta migratoria L.

Anstee, J.H.; Baldrick, Paul; Bowler, K.

doi:10.1016/0005-2736(86)90493-1

Cited by 23 publications

(2 citation statements)

References 52 publications

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“…However, K + -channels are not the exclusive entry pathway for K + . Other transport mechanisms mediating K + entry may include the Na + /K + ATPase (Anstee et al, 1986;Grieco and Lopes, 1997;Linton and O'Donnell, 1999;Xu and Marshall, 1999) and possibly KCl and Na/K/2Cl cotransport systems (Leyssens et al, 1994). Aw and Jones (1985) have hypothesized that, similar to cytosolic ATP gradients, pH gradients may exist in the cytosol, especially in cells with active proton pumps such as the V-type H + -ATPase.…”

Section: Entry Of K + From the Hemolymph Into The Cellmentioning

confidence: 99%

The dependence of electrical transport pathways in Malpighian tubules on ATP

Beyenbach

2003

Journal of Experimental Biology

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Studies of transepithelial transport typically focus on the movement of ions, organic solutes and water across the epithelium, but what drives transport is ultimately metabolism. The latter has not received much attention in studies of epithelial transport. However, metabolism and transepithelial transport must be intimately coupled, especially in actively transporting epithelia, such as Malpighian tubules. Indeed, in Malpighian tubules of the yellow fever mosquito Aedes aegypti, the inhibition of oxidative phosphorylation with dinitrophenol brings transepithelial electrolyte and water secretion immediately to a halt and eliminates voltages across cell membranes and the whole epithelium (Beyenbach, 2001).Since the product of oxidative phosphorylation is ATP, the present study was undertaken to examine the relationship between intracellular ATP concentration ([ATP]i) and electroconductive and electrogenic transport mechanisms in principal cells of Malpighian tubules of the yellow fever mosquito. Principal cells are the sites of Na + and K + secretion from the hemolymph into the tubule lumen (Beyenbach, 1995). The entry of K + into the cell from the hemolymph is electroconductive through K + -channels in the basolateral membrane ( Fig. 1). On the apical side of the cell, extrusion of K + from the cytoplasm into the tubule lumen is thought to be mediated by an nH + /K + exchanger that, in turn, is driven by the electrochemical H + potential generated across the membrane by the activity of the electrogenic V-type H + -ATPase, also located in the apical membrane. To examine the relationship between [ATP]i and electroconductive and electrogenic transport mechanisms in principal cells of the tubule, we measured the effects of metabolic inhibition on [ATP]i in one set of tubules, and the effects on membrane voltage and resistance of principal cells in another set of tubules. We found that a severe reduction in [ATP]i not only inhibited the electrogenic V-type H + -ATPase at the apical membrane but also blocked the K + -conductance of the basolateral membrane at the same time. Simultaneous changes at both apical and basolateral membranes as a function of [ATP]i suggest that ATP integrates the transport steps at these two cell membranes. In the absence of ATP synthesis, the drop of [ATP]i to 10% of control levels effectively isolates the cell

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Section: Entry Of K + From the Hemolymph Into The Cellmentioning

confidence: 99%

The dependence of electrical transport pathways in Malpighian tubules on ATP

Beyenbach

2003

Journal of Experimental Biology

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“…of a basolateral Na + /K + -ATPase in insect epithelia, this ouabain-sensitive electrogenic pump has been implicated in facilitating K + transport in Locusta (Anstee et al, 1986) and Na + transport in Rhodnius (Maddrell and Overton, 1988) tubule cells. However, fluid secretion rates of Drosophila melanogaster (Dow et al, 1994) and Formica tubules remain unaffected by ouabain and thus, if present, the Na + /K + -ATPase does not appear to play a role in fluid secretion.…”

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confidence: 99%

K+ transport in Malpighian tubules ofTenebrio molitorL.: a study of electrochemical gradients and basal K+uptake mechanisms

Wiehart

Nicolson

Kerkhove

2003

Journal of Experimental Biology

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SUMMARYMalpighian tubules of the mealworm Tenebrio molitor were isolated for intracellular measurement of basolateral (Vbl) and,indirectly, apical (Vap) membrane potentials. In control Ringer (50 mmol l-1 K+, 140 mmol l-1Na+), Vbl was 24mV, cell negative, and Vap was 48 mV, cell negative with reference to the lumen. Ion substitution experiments involving K+ and Na+indicated that both Vbl and Vap were sensitive to the bathing K+ concentration, with the change in Vap being 60-77% that of Vbl. A 10-fold drop in bath [K+] irreversibly decreased fluid secretion rates from 6.38±0.95 nl min-1 (mean ± S.E.M.) to 1.48±0.52 nl min-1 (N=8). In the presence of 6 mmol l-1 Ba2+, a blocker of basal K+ channels,fluid secretion rates reversibly decreased and the hyperpolarization of both Vbl and Vap seen in 50 mmol l-1 and 140 mmol l-1 K+ indicated a favourable electrochemical gradient for basal K+ entry. In 5 mmol l-1 K+, Ba2+ induced two different responses: Vbl either hyperpolarized by approximately 10 mV or depolarised by approximately 14mV, according to the electrochemical gradient for K+, which was either inward or outward in low bath[K+]. Rubidium, a `permeant' potassium substitute, caused a hyperpolarization of Vbl, indicating the specificity of K+ channels found in Tenebrio tubule cells. Other possible K+ uptake mechanisms located in the basolateral membrane were investigated. Blocking of the putative electroneutral Na+/K+/2Cl- cotransporter by 10 μmol l-1 bumetanide reversibly decreased fluid secretion rates, with no detectable change in membrane potentials. Ouabain (1 mmol l-1), an Na+/K+-ATPase inhibitor, irreversibly decreased fluid secretion rates but had no effect on electrical potential differences either in the absence or presence of Ba2+. The results implicate K+ channels, the Na+/K+/2Cl-contransporter and the Na+/K+-ATPase in basal K+ and fluid transport of Tenebrio tubule cells.

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Ester Hydrolases, ATPases and Carboanhydrases

Urich

1994

Comparative Animal Biochemistry

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Studies on ouabain-binding to (Na+ + K+)-ATPase from Malpighian tubules of the locust, Locusta migratoria L.

Cited by 23 publications

References 52 publications

The dependence of electrical transport pathways in Malpighian tubules on ATP

The dependence of electrical transport pathways in Malpighian tubules on ATP

K+ transport in Malpighian tubules ofTenebrio molitorL.: a study of electrochemical gradients and basal K+uptake mechanisms

Ester Hydrolases, ATPases and Carboanhydrases

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