scholarly journals INSECT MALPIGHIAN TUBULES: V-ATPase ACTION IN ION AND FLUID TRANSPORT.

1992 ◽  
Vol 172 (1) ◽  
pp. 417-429 ◽  
Author(s):  
SH Maddrell ◽  
MJ O'Donnell
Keyword(s):  
Ion Transport ◽  
Fluid Transport ◽  
Cation Transport ◽  
Malpighian Tubules ◽  
Luminal Cell ◽  
Potassium Ions ◽  
Sodium Ions ◽  
Cation Pump ◽  
Acid Fluid ◽  
Excretory Organs

Insect Malpighian tubules secrete fluid into the lumen as part of their function as excretory organs. The underlying ion transport is, when stimulated, faster than in any other known tissue. It is driven by the activity of an H+-transporting V-ATPase situated on the luminal cell membranes. This ATPase, together with cation/H+ antiporter(s), constitutes a common cation pump which can transport sodium ions, potassium ions or both. Treatments that selectively slow cation transport across the epithelium cause the secreted fluid to become alkaline, whereas those that selectively reduce the rate of anion passage lead to secretion of acid fluid.

Membrane dynamics in insect malpighian tubules

1989 ◽  
Vol 257 (5) ◽  
pp. R967-R972
Author(s):  
T. J. Bradley
Keyword(s):  
Ion Transport ◽  
Driving Force ◽  
Fluid Secretion ◽  
Membrane Dynamics ◽  
Malpighian Tubules ◽  
Membrane Insertion ◽  
Cation Pump ◽  
Active Ion Transport ◽  
Urine Formation ◽  
Apical Membranes

Urine formation in insects occurs in the Malpighian tubules by means of active ion transport and osmotically coupled water flow. The rates of urine formation can vary with time and can be modulated by diuretic hormones, developmental events, and intracellular parasitism. This paper reviews a number of recent studies in which it has been demonstrated that variations in transport rate are associated with substantial changes in tubule ultrastructure in the form of membrane insertion into and deletion from the apical microvilli. The principal driving force for fluid movement in Malpighian tubules is thought to be a common cation pump located in the apical membranes. It is proposed that modulation of the apical microvillar membrane may reflect regulation by the cells of the number of common cation pump units involved in fluid secretion.

Secretion of Hypo-osmotic Fluid by the Lower Malpighian Tubules of Rhodnius Prolixus

1975 ◽  
Vol 62 (3) ◽  
pp. 671-683 ◽  
Author(s):  
S. H. P. MADDRELL ◽  
J. E. PHILLIPS
Keyword(s):  
High Speed ◽  
Rhodnius Prolixus ◽  
Malpighian Tubules ◽  
Potassium Content ◽  
Potassium Ions ◽  
Sodium Ions ◽  
Osmotic Concentration ◽  
Concentration Difference ◽  
Rate Of Absorption ◽  
Lower Permeability

1. The ability of Rhodnius to excrete an hypo-osmotic fluid at high rates can be attributed to the activity of the lower lengths of the Malpighian tubules. 2. In the presence of a stimulant (such as 10−5 M 5-HT) they can absorb KCl from fluid in the lumen at rates as high as 0.5 μmol.min−1 cm−2. 3. The solution absorbed is strongly hyperosmotic (900 mM KCl) so that the fluid in the lumen becomes hypo-osmotic (as low as 75 mOsm) and its flow is not much slowed. 4. The rate of absorption of KCl from the lumen depends on the potassium content of fluid there; the highest rates are achieved when K-rich fluid is run through the tubule at high speed from a cannula. 5. Rubidium ions are partly effective substitutes for potassium ions in the system, but sodium ions are not absorbed at measurable rates. 6. The wall of the lower tubule has a much lower permeability to p-aminohippuric acid, xylose, sucrose and inulin than has the upper tubule -- as expected in a system able to maintain a large osmotic concentration difference.

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.

The anterior and posterior ‘stomach’ regions of larval Aedes aegypti midgut: regional specialization of ion transport and stimulation by 5-hydroxytryptamine

1999 ◽  
Vol 202 (3) ◽  
pp. 247-252 ◽  
Author(s):  
T.M. Clark ◽  
A. Koch ◽  
D.F. Moffett
Keyword(s):  
Steady State ◽  
Aedes Aegypti ◽  
Ion Transport ◽  
Malpighian Tubules ◽  
Transport Mechanisms ◽  
Regional Specialization ◽  
Negative Deflection ◽  
Electrical Polarity

The ‘stomach’ region of the larval mosquito midgut is divided into histologically distinct anterior and posterior regions. Anterior stomach perfused symmetrically with saline in vitro had an initial transepithelial potential (TEP) of −66 mV (lumen negative) that decayed within 10–15 min to a steady-state TEP near −10 mV that was maintained for at least 1 h. Lumen-positive TEPs were never observed in the anterior stomach. The initial TEP of the perfused posterior stomach was opposite in polarity, but similar in magnitude, to that of the anterior stomach, measuring +75 mV (lumen positive). This initial TEP of the posterior stomach decayed rapidly at first, then more slowly, eventually reversing the electrical polarity of the epithelium as lumen-negative TEPs were recorded in all preparations within 70 min. Nanomolar concentrations of the biogenic amine 5-hydroxytryptamine (5-HT, serotonin) stimulated both regions, causing a negative deflection of the TEP of the anterior stomach and a positive deflection of the TEP of the posterior stomach. Phorbol 12,13-diacetate also caused a negative deflection of the TEP of the anterior stomach, but had no effect on the TEP of the posterior stomach. These data demonstrate that 5-HT stimulates region-specific ion-transport mechanisms in the stomach of Aedes aegypti and suggest that 5-HT coordinates the actions of the Malpighian tubules and midgut in the maintenance of an appropriate hemolymph composition in vivo.

A Study of the Malpighian Tubules of the Pill Millipede, Glomeris marginata (Villers)

1974 ◽  
Vol 60 (1) ◽  
pp. 41-51
Author(s):  
PATRICIA ANNE FARQUHARSON
Keyword(s):  
Size Distribution ◽  
Fluid Transport ◽  
Molecular Size ◽  
Malpighian Tubules ◽  
Inverse Relation ◽  
Fluid Production ◽  
Molecular Size Distribution ◽  
Molecular Sieving ◽  
Tubule Fluid ◽  
Tubule Wall

1. Tubule fluid:medium ratios (TF/M) have been measured for inulin, glucose, LMWD and HMWD. These TF/M ratios were surprisingly high. 2. The tubule appears to act as a molecular filter; that is to say, molecules move through the tubule wall in inverse relation to their size. This is best illustrated using polyvinyl pyrrolidone as a tracer. The molecular size distribution of PVP fractions present in tubule fluid differs markedly from the molecular size distribution of PVP in the bathing Ringer. 3. No correlation can be made between the inulin and glucose TF/M and the rate of fluid production. However, the inverse relationship between TF/M and rate of fluid production for dextrans indicates a molecular sieving effect. 4. The significance of these results is discussed with reference to models of fluid transport.

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.

Sodium and Potassium Fluxes in the Abdominal Nerve Cord of the Cockroach, Periplaneta Americana L

1961 ◽  
Vol 38 (2) ◽  
pp. 315-322
Author(s):  
J. E. TREHERNE
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Nerve Cord ◽  
Periplaneta Americana ◽  
Unit Area ◽  
Potassium Ions ◽  
Sodium Ions ◽  
Nerve Sheath ◽  
The Central Nervous System ◽  
Sodium And Potassium

1. The influx of sodium and potassium ions into the central nervous system of Periplaneta americana has been studied by measuring the increase in radioactivity within the abdominal nerve cord following the injection of 24NA and 42K. into the haemolymph. 2. The calculated influx of sodium ions was approximately 320 mM./l. of nerve cord water/hr. and of potassium ions was 312 mM./l. of nerve cord water/hr. These values are very approximately equivalent to an influx per unit area of nerve cord surface of 13.9 x 10-2 M cm. -2 sec.-1 for sodium and 13.5 x 10-12 M cm. -2 sec.-1 for potassium ions. 3. The relatively rapid influxes of these ions are discussed in relation to the postulated function of the nerve sheath as a diffusion barrier. It is suggested that a dynamic steady state rather than a static impermeability must exist across the sheath surrounding the central nervous system in this insect.

Sign in / Sign up

Export Citation Format

Share Document