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.

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.

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.

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.

Unique electrophysiological effects of dinitrophenol in Malpighian tubules

1992 ◽  
Vol 263 (3) ◽  
pp. R609-R614 ◽  
Author(s):  
T. L. Pannabecker ◽  
D. J. Aneshansley ◽  
K. W. Beyenbach
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Malpighian Tubules ◽  
Membrane Voltage ◽  
Shunt Resistance ◽  
Electrophysiological Studies ◽  
Apical Membranes ◽  
Conductive Properties ◽  
Electrophysiological Effects

In the course of electrophysiological studies of Malpighian tubules of the mosquito Aedes aegypti, we have found unusual effects of 2,4-dinitrophenol (DNP) that offer new insights into the electrogenic and conductive properties of the tubule. DNP (10(-4)M) depolarized the basolateral membrane voltage from -58.0 to -3.3 mV, and it depolarized the apical membrane voltage from 110.6 to 8.9 mV. In parallel the transepithelial electrical resistance increased from 11.4 to 16.8 k omega.cm, and the fractional resistance of the apical membrane increased from 0.32 to 0.57. On the assumption that measures of transepithelial resistance in the presence of DNP approach the shunt resistance, the experimental results indicate the following characteristics for the equivalent circuit of the tubule: 1) a shunt resistance that is approximately one-half the transcellular resistance, 2) low and high electromotive forces, respectively, at the basolateral and apical membranes of principal cells, 3) an electrogenic pump at the apical membrane, and 4) a basolateral membrane voltage that is due mostly to the voltage developed by current flow across the basolateral membrane resistance.

Central role of the apical membrane H+-ATPase in electrogenesis and epithelial transport in Malpighian tubules

2000 ◽  
Vol 203 (9) ◽  
pp. 1459-1468 ◽  
Author(s):  
K.W. Beyenbach ◽  
T.L. Pannabecker ◽  
W. Nagel
Keyword(s):  
Epithelial Transport ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Coupling ◽  
Short Circuit Current ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Proton Channel ◽  
Transepithelial Transport

The effects of bafilomycin A(1), a blocker of V-type H(+)-ATPases, were investigated in Malpighian tubules of Aedes aegypti. Bafilomycin A(1) reduced rates of transepithelial fluid secretion and the virtual short-circuit current (vI(sc)) with an IC(50) of approximately 5 micromol l(−)(1). As vI(sc) decreased, the electrical resistance increased across the whole epithelium and across the apical membrane, indicating effects on electroconductive pathways. Bafilomycin A(1) had no effect when applied from the tubule lumen, pointing to the relative impermeability of the apical membrane to bafilomycin A(1). Thus, bafilomycin A(1) must take a cytoplasmic route to its blocking site in the proton channel of the H(+)-ATPase located in the apical membrane of principal cells. The inhibitory effects of bafilomycin A(1) were qualitatively similar to those of dinitrophenol in that voltages across the epithelium (V(t)), the basolateral membrane (V(bl)) and the apical membrane (V(a)) depolarized towards zero in parallel. Moreover, V(bl)always tracked V(a), indicating electrical coupling between the two membranes through the shunt. Electrical coupling allows the H(+)-ATPase to energize not only the apical membrane, but also the basolateral membrane. Furthermore, electrical coupling offers a balance between electroconductive entry of cations across the basolateral membrane and extrusion across the apical membrane to support steady-state conditions during transepithelial transport.

Vasopressin and mineralocorticoid increase apical membrane driving force for K+ secretion in rat CCD

1990 ◽  
Vol 258 (1) ◽  
pp. F199-F210 ◽  
Author(s):  
J. A. Schafer ◽  
S. L. Troutman ◽  
E. Schlatter
Keyword(s):  
Driving Force ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Voltage ◽  
Bathing Solution ◽  
Sprague Dawley ◽  
Principal Cells ◽  
Sprague Dawley Rats ◽  
K Secretion

Cortical collecting ducts (CCD) from untreated Sprague-Dawley rats were perfused and bathed in vitro with modified Krebs-Ringer solutions. Arginine vasopressin (AVP;100 microU/ml) in the bathing solution hyperpolarized the transepithelial voltage (PDT, mV) from -2.3 +/- 0.7 (control) to -6.0 +/- 1.1 (n = 22) and decreased the transepithelial resistance from 64 +/- 7 to 54 +/- 7 omega.cm2 (n = 21). AVP depolarized the basolateral membrane voltage of principal cells (PDbl) only slightly (but significantly by paired statistical comparison) from -85 +/- 1 to -84 +/- 1 mV (n = 9), with a fall in the fractional resistance of the apical membrane (FRa) from 0.82 +/- 0.03 to 0.77 +/- 0.05 (n = 9). Luminal amiloride (10 microM) produced no change in FRa in the absence of AVP, but in the presence of AVP increased FRa to the same level observed in the absence of AVP. The changes with AVP were significantly less than those observed by us previously in deoxycorticosterone (DOC)-treated animals (E. Schlatter and J. A. Schafer. Pfluegers Arch. 409:81-92, 1987), indicating that the observed synergism between DOC and AVP in stimulating Na+ absorption is attributable to a greater increase in the Na+ conductance in the apical membrane of principal cells with AVP in the DOC-treated CCD than in the normal. Furthermore, we have calculated that the depolarization of apical membrane voltage resulting from the increased Na+ conductance produced by either or both AVP and DOC increases the driving force for K+ exit across the apical membrane in proportion to the previously measured increase in secretion. This increase in driving force may be sufficient to explain the increased K+ secretion produced by these hormones with no change in the apical membrane K+ conductance.

cAMP mediates the increase in apical membrane Na+ conductance produced in rat CCD by vasopressin

1990 ◽  
Vol 259 (5) ◽  
pp. F823-F831 ◽  
Author(s):  
J. A. Schafer ◽  
S. L. Troutman
Keyword(s):  
Arginine Vasopressin ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Transepithelial Resistance ◽  
Bathing Solution ◽  
Dibutyryl Camp ◽  
Cyclic Monophosphate ◽  
Collecting Ducts ◽  
Transepithelial Voltage ◽  
Stimulation Of

Experiments were conducted to determine if adenosine 3',5'-cyclic monophosphate (cAMP) mediates the stimulation of Na+ absorption by arginine vasopressin (AVP) in isolated perfused cortical collecting ducts (CCD) from rats treated with deoxycorticosterone pivalate (5 mg im) 5-9 days before study. AVP (220 pM) in the bathing solution hyperpolarized the transepithelial voltage (PDT) from -4.0 +/- 0.8 (SE) to -15.1 +/- 1.4 mV (n = 9, P less than 0.001) and decreased the transepithelial resistance (RT) from 40 +/- 8 to 33 +/- 6 omega.cm2 (n = 5, P less than 0.025). Bath addition of 0.2 mM dibutyryl cAMP (DBcAMP), 0.1 mM isobutylmethylxanthine (IBMX), 0.1 mM DBcAMP plus 0.1 mM IBMX, and 10 or 50 microM forskolin produced the same effects, reversibly hyperpolarizing PDT by 7.0-11.5 mV and decreasing RT by 6-12 omega.cm2. Addition of 10 microM amiloride to the luminal perfusate reduced PDT from -0.9 to +2.0 mV and increased RT in the presence or absence of any of the test agents. Addition of DBcAMP + IBMX or 50 microM forskolin to the bathing solution also reversibly depolarized the basolateral membrane voltage of principal cells by 1-2 mV and decreased the apical membrane fractional resistance from 0.82-0.84 to 0.72-0.77. Both effects were reversed by addition of amiloride to the luminal perfusate. These results demonstrate that cAMP is the intracellular mediator of the increase in apical membrane Na+ conductance produced by AVP in the rat CCD.

scholarly journals The single kinin receptor signals to separate and independent physiological pathways in Malpighian tubules of the yellow fever mosquito

2010 ◽  
Vol 299 (2) ◽  
pp. R612-R622 ◽  
Author(s):  
Stephen A. Schepel ◽  
Andrew J. Fox ◽  
Jeremy T. Miyauchi ◽  
Tiffany Sou ◽  
Jason D. Yang ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Yellow Fever ◽  
Basolateral Membrane ◽  
Input Resistance ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Yellow Fever Mosquito ◽  
Electrophysiological Response ◽  
Kinin Receptor ◽  
Physiological Pathways

In the past, we have used the kinins of the cockroach Leucophaea (the leucokinins) to evaluate the mechanism of diuretic action of kinin peptides in Malpighian tubules of the yellow fever mosquito Aedes aegypti . Now using the kinins of Aedes (the aedeskinins), we have found that in isolated Aedes Malpighian tubules all three aedeskinins (1 μM) significantly 1) increased the rate of fluid secretion (V̇S), 2) hyperpolarized the basolateral membrane voltage (Vbl), and 3) decreased the input resistance (Rin) of principal cells, consistent with the known increase in the Cl− conductance of the paracellular pathway in Aedes Malpighian tubules. Aedeskinin-III, studied in further detail, significantly increased V̇S with an EC50 of 1.5 × 10−8 M. In parallel, the Na+ concentration in secreted fluid significantly decreased, and the K+ concentration significantly increased. The concentration of Cl− remained unchanged. While the three aedeskinins triggered effects on Vbl, Rin, and V̇S, synthetic kinin analogs, which contain modifications of the COOH-terminal amide pentapeptide core sequence critical for biological activity, displayed variable effects. For example, kinin analog 1578 significantly stimulated V̇S but had no effect on Vbl and Rin, whereas kinin analog 1708 had no effect on V̇S but significantly affected Vbl and Rin. These observations suggest separate signaling pathways activated by kinins. One triggers the electrophysiological response, and the other triggers fluid secretion. It remains to be determined whether the two signaling pathways emanate from a single kinin receptor via agonist-directed signaling or from a differentially glycosylated receptor. Occasionally, Malpighian tubules did not exhibit a detectable response to natural and synthetic kinins. Hypothetically, the expression of the kinin receptor may depend on developmental, nutritional, and/or reproductive signals.

scholarly journals Electrophysiological effects of basolateral [Na+] in Necturus gallbladder epithelium.

1992 ◽  
Vol 99 (2) ◽  
pp. 241-262 ◽  
Author(s):  
G A Altenberg ◽  
J S Stoddard ◽  
L Reuss
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Gallbladder Epithelium ◽  
K Channels ◽  
Necturus Gallbladder ◽  
Electrophysiological Effects ◽  
Paracellular Diffusion ◽  
Cl Conductance

In Necturus gallbladder epithelium, lowering serosal [Na+] ([Na+]s) reversibly hyperpolarized the basolateral cell membrane voltage (Vcs) and reduced the fractional resistance of the apical membrane (fRa). Previous results have suggested that there is no sizable basolateral Na+ conductance and that there are apical Ca(2+)-activated K+ channels. Here, we studied the mechanisms of the electrophysiological effects of lowering [Na+]s, in particular the possibility that an elevation in intracellular free [Ca2+] hyperpolarizes Vcs by increasing gK+. When [Na+]s was reduced from 100.5 to 10.5 mM (tetramethylammonium substitution), Vcs hyperpolarized from -68 +/- 2 to a peak value of -82 +/- 2 mV (P less than 0.001), and fRa decreased from 0.84 +/- 0.02 to 0.62 +/- 0.02 (P less than 0.001). Addition of 5 mM tetraethylammonium (TEA+) to the mucosal solution reduced both the hyperpolarization of Vcs and the change in fRa, whereas serosal addition of TEA+ had no effect. Ouabain (10(-4) M, serosal side) produced a small depolarization of Vcs and reduced the hyperpolarization upon lowering [Na+]s, without affecting the decrease in fRa. The effects of mucosal TEA+ and serosal ouabain were additive. Neither amiloride (10(-5) or 10(-3) M) nor tetrodotoxin (10(-6) M) had any effects on Vcs or fRa or on their responses to lowering [Na+]s, suggesting that basolateral Na+ channels do not contribute to the control membrane voltage or to the hyperpolarization upon lowering [Na+]s. The basolateral membrane depolarization upon elevating [K+]s was increased transiently during the hyperpolarization of Vcs upon lowering [Na+]s. Since cable analysis experiments show that basolateral membrane resistance increased, a decrease in basolateral Cl- conductance (gCl-) is the main cause of the increased K+ selectivity. Lowering [Na+]s increases intracellular free [Ca2+], which may be responsible for the increase in the apical membrane TEA(+)-sensitive gK+. We conclude that the decrease in fRa by lowering [Na+]s is mainly caused by an increase in intracellular free [Ca2+], which activates TEA(+)-sensitive maxi K+ channels at the apical membrane and decreases apical membrane resistance. The hyperpolarization of Vcs is due to increase in: (a) apical membrane gK+, (b) the contribution of the Na+ pump to Vcs, (c) basolateral membrane K+ selectivity (decreased gCl-), and (d) intraepithelial current flow brought about by a paracellular diffusion potential.

Electrophysiological evidence for Cl secretion in shark renal proximal tubules

1985 ◽  
Vol 248 (2) ◽  
pp. F282-F295 ◽  
Author(s):  
K. W. Beyenbach ◽  
E. Fromter
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
In Vitro Perfusion ◽  
Electrophysiological Properties ◽  
Electrophysiological Responses ◽  
Tubule Lumen ◽  
Transepithelial Voltage ◽  
Cl Conductance

The electrophysiology of shark proximal tubules (Squalus acanthias) was investigated using conventional microelectrodes and cable analysis. Under in vitro perfusion with symmetrical Ringer solutions, tubule transepithelial resistance was 36.3 +/- 2.3 omega X cm2 (means +/- SE, n = 44). Other electrophysiological variables varied widely under control conditions. In unstimulated tubules (n = 16) the transepithelial voltage (VT,o) was lumen positive (1.2 +/- 0.2 mV), the basolateral membrane potential (Vbl,x) was -61.3 +/- 1.6 mV, and the fractional resistance of the apical membrane (fRa) was 0.67 +/- 0.02. Spontaneously stimulated tubules (n = 28) had lumen-negative VT,o values (-1.5 +/- 0.4 mV), low Vbl,x values (-41.3 +/- 1.7 mV), and low fRa values (0.30 +/- 0.02). The stimulated state can be induced in unstimulated tubules via treatment with cAMP. Multiple microelectrode impalements in a single tubule revealed epithelial cells sharing similar electrophysiological properties. Selective ion substitutions in the tubule lumen and peritubular bath uncovered an increased Cl conductance in the apical membrane of spontaneously and cAMP-stimulated tubules. Anthracene-9-carboxylic acid tended to reverse the stimulated state, and furosemide hyperpolarized Vbl,x. These results constitute the first evidence for secretory Cl transport in a renal proximal tubule. The electrophysiological responses to ion substitutions, stimulators, and inhibitors are strikingly similar to those of known Cl-transporting epithelia.

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