An investigation into the effects of inhibitors of fluid production by Locusta Malpighian tubule Type I cells on their secretion and elemental composition

Hopkin, Richard; Anstee, J.H.; Bowler, K.

doi:10.1016/s0022-1910(00)00131-1

Cited by 5 publications

(2 citation statements)

References 42 publications

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“…Consistent with this hypothesis is the significant depolarization of the basolateral membrane voltage from 63·mV to 51·mV, reflecting the drop in the K + -diffusion potential across the basolateral membrane (Hegarty et al, 1991). Direct measurements of intracellular K + concentrations in Malpighian tubules of the locust show that furosemide, which blocks Na + /K + /2Cl -cotransport like bumetanide, causes intracellular K + concentration to fall and to be replaced by Na + (Hopkin et al, 2001). Likewise, intracellular Na + replaces K + in Malpighian tubules of Rhodnius that are stimulated to secrete Na + in the presence of serotonin (Ianowski et al, 2001).…”

Section: Stimulation Of Transepithelial Na + Secretion By Bumetanidementioning

confidence: 75%

Mechanisms of K+ transport across basolateral membranes of principal cells in Malpighian tubules of the yellow fever mosquito,Aedes aegypti

Scott

Lee

et al. 2004

Journal of Experimental Biology

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SUMMARY The mechanisms of K+ entry from the hemolymph into principal cells of Malpighian tubules were investigated in the yellow fever mosquito, Aedes aegypti. The K+ channel blocker Ba2+ (5 mmol l–1) significantly decreased transepithelial (TEP) fluid secretion (Vs) from 0.84 nl min–1 to 0.37 nl min–1 and decreased the K+ concentration in secreted fluid from 119.0 mmol l–1 to 54.3 mmol l–1 with no change in the Cl– concentration. Even though the Na+ concentration increased significantly from 116.8 mmol l–1 to 144.6 mmol l–1, rates of TEP ion secretion significantly decreased for all three ions. In addition,Ba2+ had the following significant electrophysiological effects: it depolarized the TEP voltage (Vt) from 19.4 mV to 17.2 mV,increased the TEP resistance (Rt) from 6.4 kΩcm to 6.9 kΩcm, hyperpolarized the basolateral membrane voltage of principal cells (Vbl) from –75.2 mV to –88.2 mV and increased the cell input resistance from 363.7 kΩ to 516.3 kΩ. These effects of Ba2+ reflect the block of K+ channels that, apparently, are also permeable to Na+. Bumetanide (100μmol l–1) had no effect on TEP fluid secretion and electrical resistance but significantly decreased TEP K+ secretion,consistent with the inhibition of electroneutral Na+/K+/2Cl– cotransport. TEP Na+ secretion significantly increased because other Na+entry pathways remained active. Bumetanide plus Ba2+ completely inhibited TEP electrolyte and fluid secretion, with fast and slow kinetics reflecting the Ba2+ block of basolateral membrane K+channels and the inhibition of Na+/K+/2Cl– cotransport, respectively. The single and combined effects of Ba2+ and bumetanide suggest that(1) K+ channels and Na+/K+/2Cl– cotransport are the primary mechanisms for bringing K+ into cells, (2) K+ channels mediate a significant Na+ influx, (3) Na+ has as many as four entry pathways and (4) the mechanisms of TEP K+ and Na+ secretion are coupled such that complete block of TEP K+ renders the epithelium unable to secrete Na+.

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Section: Stimulation Of Transepithelial Na + Secretion By Bumetanidementioning

confidence: 75%

Mechanisms of K+ transport across basolateral membranes of principal cells in Malpighian tubules of the yellow fever mosquito,Aedes aegypti

Scott

Lee

et al. 2004

Journal of Experimental Biology

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“…This assumption is appropriate for haemolymph samples and for fluids secreted by Malpighian tubules, both of which are of similar ionic strength to the calibration solutions used in this study. For ease of comparison with previous studies evaluating NH 4 + -selective microelectrodes (Fresser et al, 1991) and with studies in which ionic concentrations in fluids secreted by Malpighian tubules were measured by X-ray microanalysis or atomic absorption spectrophotometry (Clark and Bradley, 1996;Hopkin et al, 2001;Williams and Beyenbach, 1983), we have expressed our data in units of concentration.…”

Section: The Journal Of Experimental Biologymentioning

confidence: 99%

Ammonium secretion by Malpighian tubules ofDrosophila melanogaster: application of a novel ammonium-selective microelectrode

Browne

O’Donnell

2013

Journal of Experimental Biology

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Summary Ammonia is a toxic nitrogenous waste product of amino acid metabolism that may accumulate to high levels in the medium ingested by larvae of the fruit fly, Drosophila melanogaster. Here we report measurements of haemolymph NH4+ concentration and the secretion of NH4+ by the Malpighian (renal) tubules. Measurement of NH4+ concentrations in secreted droplets is complicated either by the requirement for large sample volumes for enzymatic assays or by the inadequate selectivity of NH4+-selective microelectrodes based on nonactin. We have developed a novel liquid membrane NH4+-selective microelectrode based on a 19-membered crown compound (TD19C6), which has been used previously in ammonium-selective macroelectrodes. In conjunction with an improved technique for correcting for interference of potassium, NH4+-selective microelectrodes based on TD19C6 permit accurate measurement of ammonium concentration in haemolymph samples and nanoliter droplets of fluid secreted by the Malpighian tubules of Drosophila melanogaster. The results indicate that active secretion of ammonium into the Malpighian tubule lumen is sufficient to maintain concentrations of approximately 1 mmol l-1 ammonium in the haemolymph of larvae reared on diets containing 100 mmol l-1 ammonium chloride.

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The Malpighian tubule: Rapid insights from post-genomic biology

Dow

Davies

2006

Journal of Insect Physiology

164

137

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An investigation into the effects of inhibitors of fluid production by Locusta Malpighian tubule Type I cells on their secretion and elemental composition

Cited by 5 publications

References 42 publications

Mechanisms of K+ transport across basolateral membranes of principal cells in Malpighian tubules of the yellow fever mosquito,Aedes aegypti

Mechanisms of K+ transport across basolateral membranes of principal cells in Malpighian tubules of the yellow fever mosquito,Aedes aegypti

Ammonium secretion by Malpighian tubules ofDrosophila melanogaster: application of a novel ammonium-selective microelectrode

The Malpighian tubule: Rapid insights from post-genomic biology

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