Preliminary isolation of mosquito natriuretic factor

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.

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Dibutyryl cAMP activates bumetanide-sensitive electrolyte transport in Malpighian tubules

AJP Cell Physiology ◽

10.1152/ajpcell.1991.261.3.c521 ◽

1991 ◽

Vol 261 (3) ◽

pp. C521-C529 ◽

Cited By ~ 66

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.

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Peptide nature of two mosquito natriuretic factors

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1986.250.3.r328 ◽

1986 ◽

Vol 250 (3) ◽

pp. R328-R332 ◽

Cited By ~ 2

Author(s):

D. H. Petzel ◽

H. H. Hagedorn ◽

K. W. Beyenbach

Keyword(s):

Biological Activities ◽

Biological Effects ◽

Gel Filtration ◽

Fluid Secretion ◽

Malpighian Tubules ◽

Peptide Bonds ◽

Polar Low ◽

Transepithelial Voltage ◽

Fraction I

High-pressure liquid chromatography (HPLC) of saline extracts of Aedes aegypti heads yields three fractions (from a total of 108) that affect transepithelial voltage and/or fluid secretion in isolated Aedes Malpighian tubules. In this study we investigated the physical and chemical nature of the active materials in these fractions. Gel-filtration chromatography revealed that the molecular weights of the three fractions were between 1,900 and 2,700. To test their thermostability the fractions were repeatedly frozen and thawed over a period of 110 days without loss of biological activity. Boiling at 100 degrees C for 5 min failed to significantly reduce their biological effects in isolated Malpighian tubules. In contrast, treatment with the proteolytic enzyme mixture, pronase, destroyed activity in all three. Fraction I no longer depolarized the transepithelial voltage of in vitro perfused Malpighian tubules, and fractions II and III completely lost their ability to stimulate fluid secretion and to affect transepithelial voltage. We conclude that our HPLC isolation yields a heterogeneous group of three polar low-molecular weight peptides. Expression of their biological activities in Malpighian tubules depends on intact peptide bonds.

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Serotonin triggers cAMP and PKA-mediated intracellular calcium waves in Malpighian tubules of Rhodnius prolixus

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00561.2013 ◽

2014 ◽

Vol 307 (7) ◽

pp. R828-R836 ◽

Cited By ~ 11

Author(s):

Paula Gioino ◽

Brendan G. Murray ◽

Juan P. Ianowski

Keyword(s):

Second Messenger ◽

Fluid Secretion ◽

Rhodnius Prolixus ◽

Malpighian Tubules ◽

Insect Vector ◽

Excess Water ◽

Intracellular Ca ◽

Single Meal ◽

Hematophagous Insect

Rhodnius prolixus is a hematophagous insect vector of Chagas disease capable of ingesting up to 10 times its unfed body weight in blood in a single meal. The excess water and ions ingested with the meal are expelled through a rapid postprandial diuresis driven by the Malpighian tubules. Diuresis is triggered by at least two diuretic hormones, a CRF-related peptide and serotonin, which were traditionally believed to trigger cAMP as an intracellular second messenger. Recently, calcium has been suggested to act as a second messenger in serotonin-stimulated Malpighian tubules. Thus, we tested the role of calcium in serotonin-stimulated Malpighian tubules from R. prolixus. Our results show that serotonin triggers cAMP-mediated intracellular Ca2+ waves that were blocked by incubation in Ca2+-free saline containing the cell membrane-permeant Ca2+ chelator BAPTA-AM, or the PKA blocker H-89. Treatment with 8-Br-cAMP triggered Ca2+ waves that were blocked by H-89 and BAPTA-AM. Analysis of the secreted fluid in BAPTA-AM-treated tubules showed a 75% reduction in fluid secretion rate with increased K+ concentration, reduced Na+ concentration. Taken together, the results indicate that serotonin triggers cAMP and PKA-mediated Ca2+ waves that are required for maximal ion transport rate.

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Dibutyryl-cAMP increases basolateral sodium conductance of mosquito Malpighian tubules

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1985.248.3.r339 ◽

1985 ◽

Vol 248 (3) ◽

pp. R339-R345 ◽

Cited By ~ 9

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.

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Both dinitrophenol and Ba2+ reduce KCl and fluid secretion in Malpighian tubules of Formica polyctena: The role of the apical H+ and K+ concentration gradient

Journal of Insect Physiology ◽

10.1016/0022-1910(93)90130-j ◽

1993 ◽

Vol 39 (12) ◽

pp. 1061-1073 ◽

Cited By ~ 11

Author(s):

A. Leyssens ◽

S.-L. Zhang ◽

E. Van Kerkhove ◽

P. Steels

Keyword(s):

Concentration Gradient ◽

Fluid Secretion ◽

Malpighian Tubules ◽

Formica Polyctena ◽

K Concentration

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Leucokinin activates Ca2+-dependent signal pathway in principal cells of Aedes aegyptiMalpighian tubules

AJP Renal Physiology ◽

10.1152/ajprenal.00041.2002 ◽

2002 ◽

Vol 283 (3) ◽

pp. F499-F508 ◽

Cited By ~ 34

Author(s):

Ming-Jiun Yu ◽

Klaus W. Beyenbach

Keyword(s):

Basolateral Membrane ◽

Malpighian Tubules ◽

Principal Cells ◽

Store Depletion ◽

Intracellular Ca ◽

Dependent Signal ◽

Transepithelial Voltage ◽

Trisphosphate Receptor ◽

Kinetics Of

The role of Ca2+ in mediating the diuretic effects of leucokinin-VIII was studied in isolated perfused Malpighian tubules of the yellow fever mosquito, Aedes aegypti. Peritubular leucokinin-VIII (1 μM) decreased the transepithelial resistance from 11.2 to 2.6 kΩ · cm, lowered the transepithelial voltage from 42.8 to 2.7 mV, and increased transepithelial Cl− diffusion potentials 5.1-fold. In principal cells of the tubules, leucokinin-VIII decreased the fractional resistance of the basolateral membrane from 0.733 to 0.518. These effects were reversed by the peritubular Ca2+-channel blocker nifedipine, suggesting a role of peritubular Ca2+and basolateral Ca2+ channels in signal transduction. In Ca2+-free Ringer bath, the effects of leucokinin-VIII were partial and transient but were fully restored after the bath Ca2+ concentration was restored. Increasing intracellular Ca2+ with thapsigargin duplicated the effects of leucokinin-VIII, provided that peritubular Ca2+ was present. The kinetics of the effects of leucokinin-VIII is faster than that of thapsigargin, suggesting the activation of inositol-1,4,5-trisphosphate-receptor channels of intracellular stores. Store depletion may then bring about Ca2+ entry into principal cells via nifedipine-sensitive Ca2+ channels in the basolateral membrane.

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