scholarly journals Functional Plasticity of the gut and the Malpighian tubules underlies cold acclimation and mitigates cold-induced hyperkalemia in Drosophila melanogaster

2017 ◽  
Author(s):  
Gil Y. Yerushalmi ◽  
Lidiya Misyura ◽  
Heath A. MacMillan ◽  
Andrew Donini
Keyword(s):  
Water Balance ◽  
Cold Acclimation ◽  
Low Temperatures ◽  
Fluid Transport ◽  
Epithelial Transport ◽  
Ion Homeostasis ◽  
Malpighian Tubule ◽  
Adult Emergence ◽  
Fluid Secretion ◽  
Malpighian Tubules

AbstractAt low temperatures, Drosophila, like most insects, lose the ability to regulate ion and water balance across the gut epithelia, which can lead to a lethal increase of [K+] in the hemolymph (hyperkalemia). Cold-acclimation, the physiological response to low temperature exposure, can mitigate or entirely prevent these ion imbalances, but the physiological mechanisms that facilitate this process are not well understood. Here, we test whether plasticity in the ionoregulatory physiology of the gut and Malpighian tubules of Drosophila may aid in preserving ion homeostasis in the cold. Upon adult emergence, D. melanogaster females were subjected to seven days at warm (25°C) or cold (10°C) acclimation conditions. The cold acclimated flies had a lower critical thermal minimum (CTmin), recovered from chill coma more quickly, and better maintained hemolymph K+ balance in the cold. The improvements in chill tolerance coincided with increased Malpighian tubule fluid secretion and better maintenance of K+ secretion rates in the cold, as well as reduced rectal K+ reabsorption in cold-acclimated flies. To test whether modulation of ion-motive ATPases, the main drivers of epithelial transport in the alimentary canal, mediate these changes, we measured the activities of Na+-K+-ATPase and V-type H+-ATPase at the Malpighian tubules, midgut, and hindgut. Na+/K+-ATPase and V-type H+-ATPase activities were lower in the midgut and the Malpighian tubules of cold-acclimated flies, but unchanged in the hindgut of cold acclimated flies, and were not predictive of the observed alterations in K+ transport. Our results suggest that modification of Malpighian tubule and gut ion and water transport likely prevents cold-induced hyperkalemia in cold-acclimated flies and that this process is not directly related to the activities of the main drivers of ion transport in these organs, Na+/K+- and V-type H+-ATPases.Summary StatementAt low temperatures, insects lose the ability to regulate ion and water balance and can experience a lethal increase in hemolymph [K+]. Previous exposure to low temperatures can mitigate this effect and improve chill tolerance. Here, we show that plasticity of ion and fluid transport across the Malpighian tubule and rectal epithelia likely drive this response.

NHE8 mediates amiloride-sensitive Na+/H+exchange across mosquito Malpighian tubules and catalyzes Na+and K+transport in reconstituted proteoliposomes

2007 ◽  
Vol 292 (5) ◽  
pp. F1501-F1512 ◽  
Author(s):  
Wanyoike Kang'ethe ◽  
Karlygash G. Aimanova ◽  
Ashok K. Pullikuth ◽  
Sarjeet S. Gill
Keyword(s):  
Fluid Transport ◽  
Ion Homeostasis ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Yeast Cells ◽  
Kinetic Properties ◽  
Sodium Load ◽  
Electrophysiological Studies ◽  
Reconstituted Membranes ◽  
Apical Membranes

Following a blood meal, the mosquito Aedes aegypti will have acquired an enormous sodium load that must be rapidly excreted to restore ion homeostasis. It is a process that demands robust sodium and fluid transport capabilities. Even though the identities of the components involved in this ion transport across the mosquito Malpighian tubule epithelia have not been completely determined, electrophysiological studies suggest the contribution of a Na+/H+exchanger extruding cations into the lumen driven secondarily by the proton gradient created by the V-type H+-ATPase in the tubules' apical membrane. We have identified the putative exchanger and designated it AeNHE8. Immunolocalization studies demonstrated that AeNHE8 is expressed in the apical membranes of Malpighian tubules, gastric caecae, and rectum. When heterologously expressed in salt-sensitive yeast cells lacking Na+extrusion and Na+/H+exchange proteins, AeNHE8 rescues the salt-sensitive phenotype and restores the cells' ability to grow in high NaCl media. Furthermore, heterologous expression of AeNHE8 in NHE-deficient fibroblast cells results in an amiloride-sensitive22Na+uptake. To determine the exchanger's kinetic properties, we reconstituted membranes from yeast cells expressing the protein into lipid proteoliposomes and assayed for cation-dependent H+exchange by fluorimetric methods. Our results indicate that AeNHE8 mediates saturable exchange of Na+and K+for H+. We propose that AeNHE8 may be coupled to the inward H+gradient across the Malpighian tubules and plays a role in the extrusion of excess sodium and potassium while maintaining steady intracellular pH in the principal cells.

Stimulation of sodium transport and fluid secretion by ouabain in an insect malpighian tubule

1988 ◽  
Vol 137 (1) ◽  
pp. 265-276 ◽  
Author(s):  
S. H. Maddrell ◽  
J. A. Overton
Keyword(s):  
Fluid Flow ◽  
Sodium Transport ◽  
Fluid Transport ◽  
Electrical Potential ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Sodium Ions ◽  
Tubule Cells ◽  
Stimulation Of

Ouabain, at all concentrations higher than 2 × 10(−7) mol l-1, stimulates the rate at which the Malpighian tubules of the insect, Rhodnius, transport sodium ions and fluid into the lumen. An effect on paracellular movement of sodium ions is unlikely because ouabain makes the electrical potential of the lumen more positive, which would slow diffusion of sodium into the lumen. Radioactive ouabain binds to the haemolymph-facing sides of the tubule cells but not to the luminal face. This binding is reduced in the presence of elevated levels of potassium or of non-radioactive ouabain. Bound ouabain is only slowly released on washing in ouabain-free saline. The evidence suggests that there is a Na+/K+-ATPase on the outer (serosal) membranes of the tubules. Such a pump would transport sodium in a direction opposed to the flow of ions and water involved in fluid transport; poisoning it with ouabain would remove this brake, and fluid flow and sodium transport would increase, as observed.

Analysis of epithelial transport by measurement of K+, Cl- and pH gradients in extracellular unstirred layers: ion secretion and reabsorption by Malpighian tubules of Rhodnius prolixus

1997 ◽  
Vol 200 (11) ◽  
pp. 1627-1638 ◽  
Author(s):  
KA Collier ◽  
MJ O'Donnell
Keyword(s):  
Epithelial Transport ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Unstirred Layer ◽  
Ph Gradients ◽  
In Situ Preparation

Summary The pH and concentrations of K+ and Cl- in the unstirred layer (USL) associated with the basolateral surfaces of the upper and lower Malpighian tubules of Rhodnius prolixus were measured using extracellular ion-selective microelectrodes. When stimulated with 5-hydroxytryptamine (5-HT) in vitro, the upper Malpighian tubule secretes Na+, K+, Cl- and water at high rates; the lower Malpighian tubule reabsorbs K+ and Cl- but not water. Concentrations of K+ and Cl- in the unstirred layer of the lower Malpighian tubule ([K+]USL, [Cl-]USL) were greater than those in the bathing saline, consistent with the accumulation of K+ and Cl- in the USL during 5-HT-stimulated KCl reabsorption. [K+]USL exceeded [K+]Bath by as much as 5.3-fold. Calculations of K+ flux based on measurements of [K+]USL at various distances from the tubule surface agreed well with flux calculated from the rate of fluid secretion and the change in K+ concentration of the secreted fluid during passage through the lower tubule. Concentrations of K+ in the unstirred layer of the upper Malpighian tubule were reduced relative to those in the bathing saline, consistent with depletion of K+ from the USL during 5-HT-stimulated secretion of K+ from bath to lumen. Changes in [K+]USL during 5-HT-stimulated K+ secretion from single upper Malpighian tubule cells could be resolved. Although differences between [K+]USL and [K+]Bath were apparent for upper and lower tubules in an in situ preparation, they were reduced relative to the differences measured using isolated tubules. We suggest that convective mixing of the fluids around the tubules by contractions of the midgut and hindgut reduces, but does not eliminate, differences between [K+]USL and [K+]Bath in situ. The USL was slightly acidic relative to the bath in 5-HT-stimulated upper and lower tubules; contributions to USL acidification are discussed. The results also show that the techniques described in this paper can resolve rapid and localized changes in ion transport across different regions of Malpighian tubules in response to stimulants or inhibitors of specific membrane transporters.

scholarly journals A unique Malpighian tubule architecture in Tribolium castaneum informs the evolutionary origins of systemic osmoregulation in beetles

2021 ◽  
Vol 118 (14) ◽  
pp. e2023314118
Author(s):  
Takashi Koyama ◽  
Muhammad Tayyib Naseem ◽  
Dennis Kolosov ◽  
Camilla Trang Vo ◽  
Duncan Mahon ◽  
...  
Keyword(s):  
Water Balance ◽  
Tribolium Castaneum ◽  
High Surface ◽  
Malpighian Tubule ◽  
Volume Ratio ◽  
Fluid Secretion ◽  
Fluorescent Labeling ◽  
Malpighian Tubules ◽  
Fluid Loss ◽  
Last Common Ancestor

Maintaining internal salt and water balance in response to fluctuating external conditions is essential for animal survival. This is particularly true for insects as their high surface-to-volume ratio makes them highly susceptible to osmotic stress. However, the cellular and hormonal mechanisms that mediate the systemic control of osmotic homeostasis in beetles (Coleoptera), the largest group of insects, remain largely unidentified. Here, we demonstrate that eight neurons in the brain of the red flour beetle Tribolium castaneum respond to internal changes in osmolality by releasing diuretic hormone (DH) 37 and DH47—homologs of vertebrate corticotropin-releasing factor (CRF) hormones—to control systemic water balance. Knockdown of the gene encoding the two hormones (Urinate, Urn8) reduces Malpighian tubule secretion and restricts organismal fluid loss, whereas injection of DH37 or DH47 reverses these phenotypes. We further identify a CRF-like receptor, Urinate receptor (Urn8R), which is exclusively expressed in a functionally unique secondary cell in the beetle tubules, as underlying this response. Activation of Urn8R increases K+ secretion, creating a lumen-positive transepithelial potential that drives fluid secretion. Together, these data show that beetle Malpighian tubules operate by a fundamentally different mechanism than those of other insects. Finally, we adopt a fluorescent labeling strategy to identify the evolutionary origin of this unusual tubule architecture, revealing that it evolved in the last common ancestor of the higher beetle families. Our work thus uncovers an important homeostatic program that is key to maintaining osmotic control in beetles, which evolved parallel to the radiation of the “advanced” beetle lineages.

THE EFFECTS OF MANDUCA SEXTA DIURETIC HORMONE ON FLUID TRANSPORT BY THE MALPIGHIAN TUBULES AND CRYPTONEPHRIC COMPLEX OF MANDUCA SEXTA

1993 ◽  
Vol 178 (1) ◽  
pp. 231-243 ◽  
Author(s):  
N. Audsley ◽  
G. M. Coast ◽  
D. A. Schooley
Keyword(s):  
Cyclic Amp ◽  
Manduca Sexta ◽  
Fluid Transport ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Hormonal Control ◽  
Malpighian Tubules ◽  
Proximal Tubules ◽  
Fluid Absorption ◽  
Diuretic Hormone

1. Manduca sexta diuretic hormone (Mas-DH) stimulates fluid secretion by adult Malpighian tubules of M. sexta, demonstrating its site of diuretic action in M. sexta for the first time. It was not possible to develop a suitable bioassay to measure fluid secretion in larval proximal tubules. 2. Mas-DH has an antidiuretic action on the cryptonephric complex of larval M. sexta because it increases fluid absorption from the rectum. It appears that in this complex Mas-DH is acting on a Na+/K+/2Cl- co-transporter, presumably on the basal membrane of the cryptonephric Malpighian tubules, because Mas-DH-stimulated fluid absorption by the cryptonephric complex is inhibited by bumetanide or the removal of Cl-, Na+ or K+ from the haemolymph side of the tissue. This is the first demonstration of hormonal control of fluid absorption by the cryptonephric complex. 3. Concomitant with the stimulation of fluid transport, Mas-DH increases the amount of cyclic AMP secreted by adult Malpighian tubules and the cryptonephric complex. In addition, Mas-DH promotes cyclic AMP production by the larval proximal tubules.

Anti-diuresis in the blood-feeding insect Rhodnius prolixus Stål: the peptide CAP2b and cyclic GMP inhibit Malpighian tubule fluid secretion.

1997 ◽  
Vol 200 (17) ◽  
pp. 2363-2367 ◽  
Author(s):  
M C Quinlan ◽  
N J Tublitz ◽  
M J O'Donnell
Keyword(s):  
Cyclic Gmp ◽  
Physiological Role ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Blood Feeding ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Tubule Fluid ◽  
Secretion Rates

Rhodnius prolixus eliminates NaCl-rich urine at high rates following its infrequent but massive blood meals. This diuresis involves stimulation of Malpighian tubule fluid secretion by diuretic hormones released in response to distention of the abdomen during feeding. The precipitous decline in urine flow that occurs several hours after feeding has been thought until now to result from a decline in diuretic hormone release. We suggest here that insect cardioacceleratory peptide 2b (CAP2b) and cyclic GMP are part of a novel mechanism of anti-diuresis. Secretion rates of 5-hydroxytryptamine-stimulated Malpighian tubules are reduced by low doses of CAP2b or cyclic GMP. Maximal secretion rates are restored by exposing tubules to 1 mmol l-1 cyclic AMP. Levels of cyclic GMP in isolated tubules increase in response to CAP2b, consistent with a role for cyclic GMP as an intracellular second messenger. Levels of cyclic GMP in tubules also increase as urine output rates decline in vivo, suggesting a physiological role for this nucleotide in the termination of diuresis.

scholarly journals Physiological and structural maturation of a polarised epithelium: the Malpighian tubules of a blood-sucking insect, Rhodnius prolixus

1990 ◽  
Vol 96 (3) ◽  
pp. 537-547
Author(s):  
H. LE B. SKAER ◽  
J. B. HARRISON ◽  
S. H. P. MADDRELL
Keyword(s):  
Fluid Transport ◽  
Physiological Function ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Second Phase ◽  
Structural Development ◽  
Blood Sucking ◽  
Late Embryogenesis ◽  
Intercellular Contacts ◽  
Two Phases

The development of polarity in a simple epithelium, the Malpighian tubules of Rhodnius, is analysed both ultrastructurally and physiologically. The onset of physiological function, including fluid secretion and the transport of solutes, is determined in late embryos and young hatchling insects and compared with structural development in tubules over a similar period. Two phases of maturation, separated by several days, are detected. The first, during late embryogenesis, involves the development of mature intercellular contacts and the dilation of the lumen, and is associated with the ability to transport specific solutes. The second phase involves the elaboration of the apical and basal membranes and the generation of mitochondria, and is associated with the onset of fluid transport in the tubules and with feeding in 4-day-old hatchlings.

Intracellular ion activities in Malpighian tubule cells ofRhodnius prolixus: evaluation of Na+-K+-2Cl-cotransport across the basolateral membrane

2002 ◽  
Vol 205 (11) ◽  
pp. 1645-1655 ◽  
Author(s):  
Juan P. Ianowski ◽  
Robert J. Christensen ◽  
Michael J. O'Donnell
Keyword(s):  
Basolateral Membrane ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Passive Movement ◽  
Malpighian Tubules ◽  
Intracellular Ion Activities ◽  
Ion Activities ◽  
Tubule Cells ◽  
Electrochemical Potentials

SUMMARYIntracellular ion activities (aion) and basolateral membrane potential (Vbl) were measured in Malpighian tubule cells of Rhodnius prolixus using double-barrelled ion-selective microelectrodes. In saline containing 103mmoll-1Na+, 6mmoll-1 K+ and 93mmoll-1Cl-, intracellular ion activities in unstimulated upper Malpighian tubules were 21, 86 and 32mmoll-1, respectively. In serotonin-stimulated tubules, aCl was unchanged, whereas aNa increased to 33mmoll-1 and aK declined to 71mmoll-1. Vbl was -59mV and -63mV for unstimulated and stimulated tubules, respectively. Calculated electrochemical potentials(Δμ/F) favour passive movement of Na+ into the cell and passive movement of Cl- out of the cell in both unstimulated and serotonin-stimulated tubules. Passive movement of K+ out of the cell is favoured in unstimulated tubules. In stimulated tubules, Δμ/F for K+ is close to 0 mV.The thermodynamic feasibilities of Na+-K+-2Cl-, Na+-Cl-and K+-Cl- cotransporters were evaluated by calculating the net electrochemical potential (Δμnet/F) for each transporter. Our results show that a Na+-K+-2Cl- or a Na+-Cl- cotransporter but not a K+-Cl- cotransporter would permit the movement of ions into the cell in stimulated tubules. The effects of Ba2+ and ouabain on Vbl and rates of fluid and ion secretion show that net entry of K+ through ion channels or the Na+/K+-ATPase can be ruled out in stimulated tubules. Maintenance of intracellular Cl- activity was dependent upon the presence of both Na+ and K+ in the bathing saline. Bumetanide reduced the fluxes of both Na+ and K+. Taken together, the results support the involvement of a basolateral Na+-K+-2Cl- cotransporter in serotonin-stimulated fluid secretion by Rhodnius prolixus Malpighian tubules.

scholarly journals Physiology, Development, and Disease Modeling in the Drosophila Excretory System

Genetics ◽  
2020 ◽  
Vol 214 (2) ◽  
pp. 235-264 ◽  
Author(s):  
Erez Cohen ◽  
Jessica K. Sawyer ◽  
Nora G. Peterson ◽  
Julian A. T. Dow ◽  
Donald T. Fox
Keyword(s):  
Human Disease ◽  
Fluid Transport ◽  
Disease Modeling ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
Excretory System ◽  
Anatomy And Physiology ◽  
Disease Biology ◽  
Organ Systems ◽  
And Function

The insect excretory system contains two organ systems acting in concert: the Malpighian tubules and the hindgut perform essential roles in excretion and ionic and osmotic homeostasis. For over 350 years, these two organs have fascinated biologists as a model of organ structure and function. As part of a recent surge in interest, research on the Malpighian tubules and hindgut of Drosophila have uncovered important paradigms of organ physiology and development. Further, many human disease processes can be modeled in these organs. Here, focusing on discoveries in the past 10 years, we provide an overview of the anatomy and physiology of the Drosophila excretory system. We describe the major developmental events that build these organs during embryogenesis, remodel them during metamorphosis, and repair them following injury. Finally, we highlight the use of the Malpighian tubules and hindgut as accessible models of human disease biology. The Malpighian tubule is a particularly excellent model to study rapid fluid transport, neuroendocrine control of renal function, and modeling of numerous human renal conditions such as kidney stones, while the hindgut provides an outstanding model for processes such as the role of cell chirality in development, nonstem cell–based injury repair, cancer-promoting processes, and communication between the intestine and nervous system.

scholarly journals A comparison of the effects of two putative diuretic hormones from Locusta migratoria on isolated locust malpighian tubules

1993 ◽  
Vol 175 (1) ◽  
pp. 1-14 ◽  
Author(s):  
G. M. Coast ◽  
R. C. Rayne ◽  
T. K. Hayes ◽  
A. I. Mallet ◽  
K. S. Thompson ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Arginine Vasopressin ◽  
Locusta Migratoria ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Enzymatic Digestion ◽  
Malpighian Tubules ◽  
Suboesophageal Ganglion ◽  
Anatomy And Physiology ◽  
Strong Stimulation

Previous work has shown that a peptide related to arginine vasopressin is present in the suboesophageal ganglion of the locust, Locusta migratoria. This peptide was determined to be an anti-parallel dimer of the nonapeptide Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-Gly-NH2 and was reported to stimulate cyclic AMP production and fluid secretion in a combined Malpighian tubules and midgut preparation from locusts. For these reasons the peptide has been called the arginine-vasopressin-like insect diuretic hormone (AVP-like IDH). Recently, a second diuretic peptide (Locusta-DP), which is related to corticotropin releasing factor, has been identified: this is a potent stimulant of fluid secretion and cyclic AMP production by isolated locust tubules. Because water balance in insects is likely to be controlled by a cocktail of hormones acting on both Malpighian tubules and hindgut, this study directly compares the activity of these two peptides in fluid secretion and cyclic AMP production bioassays on one target organ, the isolated Malpighian tubule of Locusta migratoria. Locusta-DP was synthesised directly, whereas the dimeric AVP-like IDH was obtained by oxidation of a synthetic nonapeptide monomer. Products were separated by RP-HPLC and their structures unequivocally confirmed by enzymatic digestion, sequence analysis and electrospray mass spectrometry. We show that Locusta-DP causes strong stimulation of fluid secretion and cyclic AMP production, whereas the AVP-like IDH has no effect in either assay. These findings are discussed in the light of recent work on the anatomy and physiology of the vasopressin-like immunoreactive (VPLI) neurones in the suboesophageal ganglion of Locusta migratoria, the proposed source of the AVP-like peptide.

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