Dibutyryl-cAMP increases basolateral sodium conductance of mosquito Malpighian tubules

1985 ◽  
Vol 248 (3) ◽  
pp. R339-R345 ◽  
Author(s):  
D. B. Sawyer ◽  
K. W. Beyenbach
Keyword(s):  
Basolateral Membrane ◽  
Fold Increase ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Dibutyryl Camp ◽  
Dominant Effect ◽  
Membrane Conductances ◽  
Transepithelial Voltage ◽  
K Concentration ◽  
Basolateral Membrane Potential

Dibutyryladenosine 3',5'-cyclic monophosphate (cAMP) stimulates fluid secretion in isolated Malpighian tubules of the mosquito Aedes aegypti. In the present study the effects of cAMP on the basolateral membrane were studied with conventional microelectrodes. Membrane conductances were evaluated from the changes of the basolateral membrane potential (Vbl) consequent to ion changes in the bath. Under control conditions, Vbl measured -65.2 +/- 1.5 mV [83 impalements, 67 tubules]. A fivefold decrease in the bath Na concentration hyperpolarized Vbl by 10.2 +/- 0.6 mV [7], whereas a 4.4-fold increase in the bath K concentration depolarized Vbl by 7.9 +/- 1.0 mV [9]. In the presence of cAMP (10(-4) M) Vbl depolarized to -24.8 +/- 2.7 mV [9]. Vbl now hyperpolarized by 22.7 +/- 1.5 mV [7] for the bath Na change and depolarized by only 3.8 +/- 1.1 mV [6] for the bath K change. Thus the dominant effect of cAMP is the increase of the basolateral membrane Na conductance. This increase is consistent with 1) the depolarization of Vbl and 2) the hyperpolarization of the transepithelial voltage, the decrease of the transepithelial resistance, and the increase of Na and fluid secretion observed previously. Spontaneous oscillations of Vbl were observed and could not be attributed to cyclical changes of the basolateral membrane Na conductance.

Dibutyryl cAMP activates bumetanide-sensitive electrolyte transport in Malpighian tubules

1991 ◽  
Vol 261 (3) ◽  
pp. C521-C529 ◽  
Author(s):  
J. L. Hegarty ◽  
B. Zhang ◽  
T. L. Pannabecker ◽  
D. H. Petzel ◽  
M. D. Baustian ◽  
...  
Keyword(s):  
Yellow Fever ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Fluid Secretion ◽  
Ringer Solution ◽  
Malpighian Tubules ◽  
Membrane Voltage ◽  
Dibutyryl Camp ◽  
K Secretion ◽  
Transepithelial Voltage

The effects of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) and bumetanide (both 10(-4) M) on transepithelial Na+, K+, Cl-, and fluid secretion and on tubule electrophysiology were studied in isolated Malpighian tubules of the yellow fever mosquito Aedes aegypti. Peritubular DBcAMP significantly increased Na+, Cl-, and fluid secretion but decreased K+ secretion. In DBcAMP-stimulated tubules, bumetanide caused Na+, Cl-, and fluid secretion to return to pre-cAMP control rates and K+ secretion to decrease further. Peritubular bumetanide significantly increased Na+ secretion and decreased K+ secretion so that Cl- and fluid secretion did not change. In bumetanide-treated tubules, the secretagogue effects of DBcAMP are blocked. In isolated Malpighian tubules perfused with symmetrical Ringer solution, DBcAMP significantly hyperpolarized the transepithelial voltage (VT) and depolarized the basolateral membrane voltage (Vbl) with no effect on apical membrane voltage (Va). Total transepithelial resistance (RT) and the fractional resistance of the basolateral membrane (fRbl) significantly decreased. Bumetanide also hyperpolarized VT and depolarized Vbl, however without significantly affecting RT and fRbl. Together these results suggest that, in addition to stimulating electroconductive transport, DBcAMP also activates a nonconductive bumetanide-sensitive transport system in Aedes Malpighian tubules.

Hormone-controlled cAMP-mediated fluid secretion in yellow-fever mosquito

1987 ◽  
Vol 253 (5) ◽  
pp. R701-R711 ◽  
Author(s):  
D. H. Petzel ◽  
M. M. Berg ◽  
K. W. Beyenbach
Keyword(s):  
Yellow Fever ◽  
Natriuretic Peptides ◽  
Basolateral Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
In Vivo Studies ◽  
Intracellular Camp ◽  
Yellow Fever Mosquito ◽  
Water Fraction

Evidence is presented for hormone-controlled adenosine 3',5'-cyclic monophosphate (cAMP)-mediated NaCl diuresis in Malpighian tubules of the blood-feeding yellow-fever mosquito Aedes aegypti. Studies in isolated Malpighian tubules reveal that cAMP added to the peritubular bath selectively stimulates NaCl secretion and not KCl secretion by increasing the Na conductance of the basolateral membrane of primary cells. These effects are duplicated by forskolin and theophylline in parallel with increased intracellular concentrations of endogenous cAMP. Two natriuretic peptides that we have isolated by high-pressure liquid chromatography (HPLC) methods from mosquito heads also increase NaCl and fluid secretion in isolated Malpighian tubules together with increased intracellular levels of cAMP. These results are consistent with a mechanism of NaCl diuresis in which the natriuretic peptides and cAMP are respectively the primary and secondary messengers that couple the ingestion of a blood meal to the excretion of the unwanted salt and water fraction of the meal. This hypothesis is supported by in vivo studies that reveal elevated intracellular cAMP levels in Malpighian tubules at the time of maximum NaCl diuresis.

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.

Preliminary isolation of mosquito natriuretic factor

1985 ◽  
Vol 249 (4) ◽  
pp. R379-R386 ◽  
Author(s):  
D. H. Petzel ◽  
H. H. Hagedorn ◽  
K. W. Beyenbach
Keyword(s):  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Reverse Phase Hplc ◽  
Saline Extract ◽  
Natriuretic Factor ◽  
K Secretion ◽  
Transepithelial Voltage ◽  
Nacl Secretion ◽  
Fraction I

A natriuretic factor that triggers diuresis in isolated Malpighian tubules of the mosquito was isolated from the head of the yellow-fever mosquito Aedes aegypti by passing a saline extract of mosquito heads through low-pressure and then high-pressure liquid chromatography (HPLC) columns. Three fractions with biologic activity eluted during a reverse-phase HPLC linear acetonitrile gradient run. Fraction I depolarized the transepithelial voltage (Vt) of isolated perfused Malpighian tubules but did not not stimulate fluid secretion in the Ramsay assay (J. A. Ramsay, J. Exp. Biol. 31: 104–113, 1954). Fraction II depolarized and fraction III hyperpolarized Vt, and both stimulated fluid secretion three- to fourfold. Even though the effects of fractions II and III on Vt differed, both stimulated fluid secretion by increasing the rate of NaCl secretion without affecting K secretion. The selective stimulation of active secretory Na transport by fraction III is mimicked by cyclic AMP (cAMP), suggesting the second messenger role of cAMP in the effects of fraction III. Because fraction III stimulates a NaCl-rich, as opposed to KCl-rich, fluid, the term mosquito natriuretic factor is proposed for this active fraction.

Potassium transport across basolateral membrane of acinar cells in the perfused rat pancreas

1991 ◽  
Vol 261 (4) ◽  
pp. G570-G577
Author(s):  
T. Ishikawa ◽  
T. Kanno
Keyword(s):  
Basolateral Membrane ◽  
Acinar Cells ◽  
Fluid Secretion ◽  
Potassium Transport ◽  
Perfused Rat Pancreas ◽  
Complete Replacement ◽  
Rat Pancreas ◽  
Initial Transient ◽  
K Concentration ◽  
K Transport

Efflux and influx of K+ across the basolateral membrane of acinar cells were continuously computed from the change in K+ concentration in the perfusate collected from the portal vein of the isolated perfused rat pancreas. Continuous stimulation with different concentrations of COOH-terminal octapeptide of cholecystokinin (CCK-8) caused characteristic patterns of K+ flux and fluid secretion as follows: 1) stimulation with 10 pM CCK-8 induced a gradual and small increase in K+ influx and sustained fluid secretion; 2) stimulation with 100 pM CCK-8 caused an initial transient K+ efflux followed by a secondary slow K+ influx and sustained fluid secretion; 3) stimulation with 1 nM CCK-8 also induced an initial transient K+ efflux followed by a secondary slow K+ influx, whereas there was only a slight transient increase in fluid secretion. Ouabain abolished the CCK-8-induced K+ influx, but furosemide had little, if any, effect on the CCK-8-induced K+ flux and fluid secretion. Complete replacement of Cl- with equimolar NO3- had little effect on the CCK-8-induced K+ influx. These results suggest that CCK-8 activates not only passive K+ transport but also an ouabain sensitive Na(+)-K+ pump and that the furosemide-sensitive Na(+)-K(+)-2Cl- symport may not play a significant role in CCK-8-induced K+ transport.

Relation of membrane potential to basolateral TEA transport in isolated snake proximal renal tubules

1995 ◽  
Vol 268 (6) ◽  
pp. R1539-R1545 ◽  
Author(s):  
Y. K. Kim ◽  
W. H. Dantzler
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Potent Inhibitor ◽  
Basolateral Membrane ◽  
Potential Difference ◽  
Renal Tubules ◽  
K Concentration ◽  
Electrochemical Equilibrium ◽  
Membrane Potential Difference ◽  
Basolateral Membrane Potential

We measured the effects of changes in bath K+ concentration ([K+]) on basolateral membrane potential difference (PD) and [3H]tetraethylammonium (TEA) transport in isolated snake (Thamnophis) proximal renal tubules (25 degrees C; pH 7.4). Increasing bath [K+] from 3 to 65 mM decreased PD from -60 mV (inside of cells negative) to -20 mV and 2-min uptake of [3H]TEA by approximately 25%, indicating that PD influences TEA entry into the cells. Uptake of [3H]TEA was inhibited similarly at both K+ concentrations by unlabeled TEA, indicating that uptake is carrier mediated. Kt (approximately 18 microM) for 2-min uptake of [3H]TEA in 3 mM K+ increased significantly in 65 mM K+, suggesting that the decrease in PD or the increase in [K+] alters the affinity of the transporter for TEA. The steady-state cell-to-bath ratio for [3H]TEA with 3 mM K+ (-60 mV PD) was approximately 16, significantly above the ratio of 10 predicted for passive distribution at electrochemical equilibrium. With 65 mM K+ (-20 mV PD) this ratio decreased to approximately 6, again significantly above the predicted ratio of 2. These data suggest that the PD can account for much, but not all, of the steady-state uptake of TEA. Efflux of [3H]TEA across the basolateral membrane was identical with either 3 or 65 mM K+ in the bath but was almost completely inhibited in either case by tetrapentylammonium, a potent inhibitor of TEA uptake. These data indicate that virtually all TEA transport across the basolateral membrane is carrier mediated and that transport out of the cells is unaffected by PD.

Conductive properties of papillary surface epithelium

1994 ◽  
Vol 266 (2) ◽  
pp. F259-F265 ◽  
Author(s):  
W. B. Reeves
Keyword(s):  
Cell Membrane ◽  
Apical Membrane ◽  
Ussing Chamber ◽  
Basolateral Membrane ◽  
Transepithelial Resistance ◽  
Surface Epithelium ◽  
Renal Papilla ◽  
Transepithelial Voltage ◽  
K Concentration ◽  
Conductive Properties

The surface epithelium of rabbit renal papilla was dissected free from its supporting tissue and mounted in an Ussing chamber. The conductive properties of the epithelium and of the apical and basolateral cell membranes were examined with KCl-filled microelectrodes. The transepithelial voltage was 0.07 +/- 0.15 mV, and the transepithelial resistance was 107 +/- 15 omega.cm2 (n = 29). The fractional resistance of the apical membrane (fRa) was 0.93 +/- 0.01 (n = 103 cells, 29 tissues). The apical membrane was not conductive to Na+, K+, or Cl-. An increase in the K+ concentration of the basolateral solution from 5 to 50 mM depolarized the basolateral membrane voltage (Vb) from -59 +/- 1.6 to -31.2 +/- 2.2 mV (n = 28 cells) and increased fRa from 0.935 +/- 0.01 to 0.962 +/- 0.01 (P < 0.001, n = 21 cells). Likewise, 5 mM barium in the basolateral solution depolarized Vb from -57.7 +/- 2.0 to -29.8 +/- 2.2 mV (n = 21 cells). A tenfold decrease in the Cl- concentration of the basolateral solution caused an 8.3 +/- 1.9 mV depolarization in Vb. Thus the basolateral cell membrane is conductive to K+ and Cl-. Exposure of the apical membrane to amphotericin B demonstrated that the transepithelial resistance is determined primarily by the paracellular pathway.

Chloride movement across basolateral membrane of Necturus gallbladder epithelium

1984 ◽  
Vol 247 (5) ◽  
pp. C495-C500 ◽  
Author(s):  
R. S. Fisher
Keyword(s):  
Basolateral Membrane ◽  
Membrane Voltage ◽  
Gallbladder Epithelium ◽  
Necturus Gallbladder ◽  
Concentration Changes ◽  
The Difference ◽  
K Concentration ◽  
Low Ionic Strength ◽  
Basolateral Membrane Potential

The relative Cl- and K+ sensitivity of the basolateral membrane potential of the in vitro Necturus gallbladder epithelium was determined. Tissues were punctured with two conventional glass microelectrodes to simultaneously measure the intracellular voltage (Vcs) and the voltage across the subepithelial connective tissue (Vse). Increasing the serosal K+ concentration from 2.5 to 25 mM caused a rapid monotonic depolarization of Vcs without changes of Vse. Reduction of serosal Cl- concentration (98 to 8 mM) caused a transient change of Vse. Thus the difference between Vcs and Vse more accurately reflected the basolateral membrane voltage (Vc) after Cl- concentration changes. The changes of Vc were small and biphasic in response to the decrease of serosal Cl- concentration. Perfusion of a low-ionic-strength solution in the mucosal chamber decreased the current that normally passes through the epithelium. Consistent with the notion that the basolateral voltage changes are attenuated by parallel pathways, the K+-induced depolarization increased by 80% under these conditions. The changes of Vc in response to Cl- substitutions were not different from those of tissue bathed in control solution. Thus the basolateral membrane voltage is relatively insensitive to changes of serosal Cl- concentration. I conclude that Cl- movement across the basolateral membrane is not attributable to simple electrodiffusion, and Cl- exit from these cells at this membrane must be electroneutral.

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.

ADH increases apical Na+, K+, 2Cl- entry in mouse medullary thick ascending limbs of Henle

1987 ◽  
Vol 252 (1) ◽  
pp. F177-F187 ◽  
Author(s):  
D. A. Molony ◽  
W. B. Reeves ◽  
S. C. Hebert ◽  
T. E. Andreoli
Keyword(s):  
Antidiuretic Hormone ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Mouse Kidney ◽  
Membrane Conductances ◽  
Transepithelial Voltage

These studies were designed to evaluate the mechanism for the ADH-dependent increase in transcellular conductance (Gc, mS X cm-2), which accompanies hormone-dependent increases in the spontaneous transepithelial voltage (Ve, mV) and in the net rate of Cl- absorption in single medullary thick ascending limbs of Henle (mTALH) isolated from mouse kidney. The total transepithelial conductance (Ge, mS X cm-2) was measured with perfusing solutions containing 5 mM K+, zero Ba2+; Gc was that component of Ge blocked by luminal 20 mM Ba2+, zero K+. In paired experiments, antidiuretic hormone (ADH) increased Gc from 44.5 +/- 5.6 to 58.9 +/- 8.9 mS X cm-2 (delta = 14.3 +/- 5.5; P less than 0.02); however, in the presence of 10(-4) M luminal furosemide, ADH had no significant effect on Gc (delta = 5.0 +/- 4.3; NS). A set of similarly paired measurements together with paired observations on the effects of bath Cl- deletion, permitted an assessment of the effect of ADH on the magnitude of the fall in Gc on bath Cl- removal (delta GClc, mS X cm-2). delta GClc was clearly larger with ADH, 29.6 +/- 4.3, than without ADH, 19.2 +/- 1.0 (delta = 10.4 +/- 4.9; P less than 0.05). However, with luminal furosemide, ADH had no significant effect on delta GClc (delta = 1.7 +/- 4.5; NS). These results indicate that the ADH-dependent increase in Gc is secondary to increased salt entry across the apical membrane. We computed apical (ga, mS X cm-2) and basolateral (gb, mS X cm-2) membrane conductances from the Gc measurements and apical-to-basolateral membrane resistance ratios (Ra/Rb) obtained from cell impalement: the ADH-dependent Gc increase was due to an increase in gb, which was blocked entirely by luminal furosemide. We propose that ADH increases the number of functioning apical membrane Na+,K+,2Cl- transport units, and that gb increases because cell Cl- activity rises and depolarizes the basolateral membrane. Thus the calculated cellular Cl- activity was 16.3 mM without ADH, and 25 mM with ADH.

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