Active transport of sodium by the malpighian tubules of the tsetse fly Glossian morsitans

1976 ◽  
Vol 64 (2) ◽  
pp. 357-368
Author(s):  
J. D. Gee
Keyword(s):  
Cell Function ◽  
Malpighian Tubule ◽  
Active Role ◽  
Fluid Secretion ◽  
Sodium Concentration ◽  
Tsetse Fly ◽  
Malpighian Tubules ◽  
Bathing Solution ◽  
Bathing Medium

Isolated Malpighian tubules of Glossina morsitans are able to transport sodium against its concentration gradient. Their rate of secretion is dependent on the sodium concentration of the bathing medium. Potassium must be present in the bathing solution for rapid secretion to be maintained, but it does not play an active role in fluid secretion. Lithium and ammonium ions are able to substitute partially for sodium, other monovalent cations cannot. Ouabain does not affect rapid secretion by Glossina tubules in vitro. Conclusions drawn from the results are incorporated into a model of Malpighian tubule cell function in this insect.

scholarly journals Excretion in the House Cricket (Acheta Domesticus): Stimulation of Diuresis by Tissue Homogenates

1987 ◽  
Vol 129 (1) ◽  
pp. 63-81 ◽  
Author(s):  
JEFFREY H. SPRING ◽  
SHELIA R. HAZELTON
Keyword(s):  
Lethal Dose ◽  
Fluid Secretion ◽  
Sodium Concentration ◽  
Inhibitory Effect ◽  
Acheta Domesticus ◽  
Malpighian Tubules ◽  
Secretion Rate ◽  
Tissue Homogenates ◽  
Extreme Sensitivity

1. A new method is described for maintaining cricket Malpighian tubules in vitro. Warmed, oxygenated saline is circulated rapidly past the tubules, while the secreted urine is collected under oil for analysis. This technique allows the cricket tubules to be observed and manipulated for extended periods (6 h), in contrast to their short life (>1 h) using conventional methods. 2. Cricket tubules show extreme sensitivity to oxygen deprivation, such that 15 min of anoxia represents the median lethal dose (LD50) for in vitro preparations. 3. Homogenates of corpus cardiacum (CC) cause the rate of fluid secretion by the tubules to double. The maximum stimulation is dose-dependent over the range 0.01 to 1.0 CC. Homogenates of brain and other ganglia show much smaller stimulatory effects (0.01-0.02 CC-equivalents). Cyclic AMP mimics the increase in secretion rate, but has an inhibitory effect on the smooth muscle of the ureter. 4. Control preparations maintain a urine osmotic pressure (OP) that is hyperosmotic to the bath by 5–10 mosmol l−1. CC homogenate produces a decrease in urine OP to 10–12 mosmol l−1 hypo-osmotic to the bath. This suggests that active solute reabsorption is occurring in the lower tubule or ampulla. 5. Stimulation by CC homogenate increases the urine potassium concentration slightly less than two-fold, whereas the sodium concentration increases by a maximum of five-fold and remains at a higher concentration than potassium throughout the experiment. Tubule secretion rate is drastically inhibited in nominally sodium-free saline.

scholarly journals Transport of Uric Acid by the Malpighian Tubules of Rhodnius Prolixus and Other Insects

1983 ◽  
Vol 103 (1) ◽  
pp. 169-184 ◽  
Author(s):  
M.J. O'DONNELL ◽  
S. H.P. MADDRELL ◽  
B. O.C. GARDINER
Keyword(s):  
Uric Acid ◽  
Malpighian Tubule ◽  
Tsetse Fly ◽  
Malpighian Tubules ◽  
Electrochemical Gradient ◽  
Direct Response ◽  
Urate Transport ◽  
Surrounding Fluid

Urate is transported against an electrochemical gradient into the lumen of the lower Malpighian tubule of Rhodnius. In vivo, higher urate transport rates are induced by the increase in haemolymph urate concentration that follows feeding. The induced rate of transport is sufficient to account for the amount of urate eliminated. In vitro experiments with the tsetse fly Glossina suggest a possible induction of transport as a direct response of the tubule cells to an increase in urate concentration in the surrounding fluid. Urate transport has been shown for Malpighian tubules of insects from several different orders, suggesting that the mechanism is widespread. Insect urate transport differs from that of vertebrates; it is ouabain-insensitive and results in the precipitation of free uric acid instead of urate salts.

Fluid secretion by the malpighian tubules of the tsetse fly Glossina morsitans: the effects of ouabain, ethacrynic acid and amiloride

1976 ◽  
Vol 65 (2) ◽  
pp. 323-332
Author(s):  
J. D. Gee
Keyword(s):  
Sodium Transport ◽  
Cardiac Glycoside ◽  
Ethacrynic Acid ◽  
Fluid Secretion ◽  
Sodium Concentration ◽  
Tsetse Fly ◽  
Malpighian Tubules ◽  
Sodium Ions ◽  
Glossina Morsitans ◽  
Sodium And Potassium

The effects of three inhibitors of sodium transport on the secretion of fluid by the Malpighian tubules of Glossina morsitans have been observed. The cardiac glycoside, ouabain, affects neither the rate of secretion nor the sodium concentration of the fluid secreted when isolated tubules are bathed by solutions containing a range of sodium and potassium concentrations. Secretion is inhibited, however, by ethacrynic acid and amiloride. The results confirm that fluid secretion by the Malpighian tubules of this insect is dependent on the active transport of sodium ions and show that Na+/k+ exchange pumps are not involved in this process.

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.

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.

Fluid secretion in the nephron: Relation to renal failure

1976 ◽  
Vol 56 (1) ◽  
pp. 248-258 ◽  
Author(s):  
J. J. Grantham
Keyword(s):  
Fluid Transport ◽  
Fluid Secretion ◽  
Cystic Kidney Disease ◽  
Rabbit Kidney ◽  
Cystic Kidney ◽  
Obstructive Nephropathy ◽  
Bathing Medium ◽  
Pars Recta ◽  
Uremic Syndrome

It had been generally accepted that glomerular filtration and tubular reabsorption were the basic modes of fluid transport in mammalian nephrons. Recently, evidence was obtained to indicate that net fluid secretion may occur in mammalian nephrons as well. In the pars recta portion of proximal tubules of rabbit kidney net fluid secretion was observed in vitro in response to PAH and other aryl acids in the peritubular bathing medium. Net fluid secretion appeared to be coupled to the transcellular transport of aryl acid from bath to lumen. Serum from uremic subjects stimulated net fluid secretion in the pars recta in a manner similar to PAH. The accumulation of high levels of endogenous aryl acids may contribute to the general organ dysfunction that is a part of the uremic syndrome of advanced renal insufficiency. Futhermore, there is evidence to suggest that the fluid-secretion phenomenon in association with aryl acids may significantly affect renal excretion and morphology in slow-flow states, in patients with cystic kidney disease, and in obstructive nephropathy.

Transepithelial and intracellular potentials in isolated Malpighian tubules of tenebrionid beetle

1987 ◽  
Vol 252 (4) ◽  
pp. F645-F653 ◽  
Author(s):  
S. W. Nicolson ◽  
L. C. Isaacson
Keyword(s):  
Membrane Potential ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Bathing Medium ◽  
Intracellular Potentials ◽  
Tenebrionid Beetle ◽  
Fold Reduction ◽  
K Concentration ◽  
Opposing Effects

Malpighian tubules of Onymacris plana (Coleoptera: Tenebrionidae) have been isolated for measurement of transepithelial and intracellular potentials, before and during stimulation of fluid secretion. In a bathing medium resembling the hemolymph composition of the insect, the transepithelial potential (VT) was approximately 13 mV, lumen positive. VT was subject to drift and frequently showed super-imposed regular oscillations, which were apparently action potentials associated with contractions of muscle fibers running along the tubules. Although tubules of Onymacris are approximately 8 cm long, the basal membrane potential (Vb) did not vary with distance along the tubule, averaging -31 mV. Addition of adenosine 3',5'-cyclic monophosphate (cAMP) or diuretic hormone (DH) homogenate to the bathing medium had no effect on Vb, but opposing effects on VT: cAMP caused it to increase to 60 mV, whereas DH homogenate caused a rapid drop in VT to almost zero. Ion substitutions in the bathing medium showed that under control conditions beetle tubules possessed appreciable basal permeability to both K and Cl ions, with a 10-fold reduction in bath K concentration hyperpolarizing Vb by 54 mV. The basal K and Cl channels were partially blocked by barium and thiocyanate ions, respectively. Stimulation with cAMP increased the apical membrane potential (Va) and significantly reduced the Cl permeability of the basal membrane, whereas its Na permeability remained negligible.

Secretion of endolymph by semicircular canals of the shark

1988 ◽  
Vol 255 (4) ◽  
pp. F711-F719 ◽  
Author(s):  
J. L. Garvin ◽  
K. R. Spring ◽  
P. A. Santi
Keyword(s):  
Semicircular Canals ◽  
Fluid Secretion ◽  
Cell Types ◽  
Constant Current ◽  
K Channel ◽  
Bathing Solution ◽  
Cation Selectivity ◽  
Tissue Resistance ◽  
K Concentration

The semicircular canals of the vestibular labyrinth of the dogfish shark, Squalus acanthias, may serve as a simple in vitro system for the study of the ionic transport mechanisms involved in endolymph formation. Electron microscopy showed that the epithelium was made up of at least three distinct cell types divided into separate regions running the length of the canals. Secretion of endolymph was studied in isolated canals by the split droplet method; when the lumens of the canals were filled with shark Ringer a potassium-rich fluid was secreted into the lumen at a rate of 0.34 microliter.cm-2.min-1. The K concentration of the secreted fluid averaged 112 mM; the calculated rate of K secretion was 2.3 mumol.cm-2.h-1, comparable to recent measurements in mammalian utricle. Fluid secretion was dependent on active transport and was inhibited by ouabain, bumetanide, or methazolamide in the external bathing solution. Fluid secretion was unaffected by the K channel blocker, Ba, in the luminal droplet or by the adenylate cyclase stimulator, forskolin, in the external bathing solution. For electrophysiological analysis, isolated canals were perfused in a chamber designed for voltage/current clamping; an axial wire was inserted into the canal lumen and constant-current pulses were passed to determine tissue resistance. When the luminal fluid was high-K Ringer, transepithelial potential difference was -1.1 mV (lumen negative) and resistance 37 omega.cm2. Dilution and bi-ionic potential measurements showed that the epithelium of the canals exhibited only slight cation selectivity. These results are consistent with a model for endolymph secretion involving cotransport secondary to the ion gradients created by the Na+-K+-ATPase.

scholarly journals Secretion by the Malpighian tubules of Rhodnius prolixus stal: electrical events

1984 ◽  
Vol 110 (1) ◽  
pp. 275-290 ◽  
Author(s):  
M. J. O'Donnell ◽  
S. H. Maddrell
Keyword(s):  
Apical Membrane ◽  
Electrical Response ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Chloride Permeability ◽  
Bathing Medium ◽  
Before And After ◽  
Electrical Gradient ◽  
Cation Pump

Transepithelial and intracellular potentials have been simultaneously recorded from Rhodnius upper Malpighian tubules before and after stimulation of fluid secretion. The transepithelial electrical response to the diuretic hormone mimic 5-hydroxytryptamine (5-HT) was triphasic; recordings of intracellular potential changes indicated that the three phases represented successive events at the apical membrane. Depolarizations produced by increasing the bathing medium potassium concentration indicated that the basal membrane was much more permeable to potassium than to sodium. Electrical responses to chloride-free saline were inconsistent with a significant basal membrane chloride permeability. Chloride movements across the basal membrane were opposed by an electrical gradient of about 65 mV. The results of experiments in which tubules were exposed to chloride-free saline or sodium-free saline suggested that chloride entry into the cells was linked to the entry of Na+ and K+. The effects of furosemide and bumetanide upon secretion and potential changes suggested that chloride crossed the basal membrane through co-transport with Na+ and K+. Chloride probably crosses the apical membrane into the lumen passively in response to a favourable electrical gradient of about 35 mV. Cations must be actively pumped into the lumen against an electrical gradient of 35 mV. Our results support previous evidence for an apical cation pump which actively transports Na and K into the lumen. A tentative model of ionic movements during fluid secretion is presented. It is suggested that the apical cation pump maintains sodium at low intracellular concentrations, thereby maintaining a favourable gradient for entry of Na+ through the proposed basal co-transport step. The suggested stoichiometry is Na+:K+:2 Cl-.

scholarly journals Action of activated 27,000 Mr toxin from Bacillus thuringiensis var. israelensis on Malpighian tubules of the insect, Rhodnius prolixus

1989 ◽  
Vol 94 (3) ◽  
pp. 601-608
Author(s):  
S.H. Maddrell ◽  
J.A. Overton ◽  
D.J. Ellar ◽  
B.H. Knowles
Keyword(s):  
Bacillus Thuringiensis ◽  
Cell Membrane ◽  
Basal Cell ◽  
Time Course ◽  
Fluid Secretion ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Bathing Solution ◽  
Concentrated Solutions ◽  
Intracellular Milieu

The action of activated 27,000 Mr toxin from Bacillus thuringiensis var. israelensis (Bti toxin) on Malpighian tubules of Rhodnius prolixus has been investigated. Its binding to the tubules is slowed by low temperature but is not prevented even at 0 degree C. The binding is less effective at pH 10 than at pH7. Pretreatment of the tubules with 0.1 mmol l-1 ouabain or bumetanide or 1 mumol l-1 5-hydroxytryptamine did not affect the toxicity of the toxin. The toxin causes very large changes in the trans-epithelial potential difference; it changes from 40 mV, lumen negative, often to more than 100 mV, lumen positive. This reflects an initial collapse of the potential of the basal cell membrane, followed by a large positive-going potential change at the luminal cell membrane. Just prior to the effects of the toxin on rapid fluid secretion, the basal cell membrane becomes permeable to sucrose molecules. Raffinose at 170 mmol l-1 in the bathing solution does not protect the tubules from Bti toxin action but dextran, Mr5000, at 60 mmol l-1 significantly delayed failure of fluid secretion and, even more, the onset of staining of the tubule cells with Trypan Blue. Exposing tubules to saline that is calcium-free and/or magnesium-free, or has a composition adjusted to be similar to that of the intracellular milieu, does not affect the time course of failure of fluid secretion induced by the toxin. There is no evidence that effective aggregates of Bti toxin molecules are formed in concentrated solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

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