Optical Quantification of Intracellular pH in <em>Drosophila melanogaster </em>Malpighian Tubule Epithelia with a Fluorescent Genetically-encoded pH Indicator

Intracellular pH was measured in bullfrog gastric mucosa using a pH-indicator dye, bromthymol blue (BTB), with a spectrophotometric technique. Studies showed that BTB is taken up by the gastric mucosa and bound to intracellular components. The binding of BTB was shown to cause a shift in the pKa of the dye from the solution value of 6.95 to a value of 8.0. During the nonsecreting state, intracellular pH was estimated to be 7.4 (metiamide inhibition) or 7.1 (SCN inhibition). During active secretion of acid, intracellular pH increased with increasing secretion rates, reaching values in excess of pH 8. Using preparations from which the surface epithelial cells had been removed, it was shown that at least a portion of the alkaline response to stimulation occurs in the oxyntic or tubular cells. The results are interpreted in view of existing models for the chemical reaction involved in gastric acid secretion.

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Assays of Intracellular pH Using Chemical Probes: Principles of the pH Indicator Response

Intracellular pH and Its Measurement ◽

10.1201/9781003068266-4 ◽

2020 ◽

pp. 37-49

Author(s):

Jan Slavík

Keyword(s):

Intracellular Ph ◽

Chemical Probes ◽

Ph Indicator

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An increase in intracellular pH during neural induction in Xenopus

Development ◽

10.1242/dev.120.2.433 ◽

1994 ◽

Vol 120 (2) ◽

pp. 433-442 ◽

Cited By ~ 1

Author(s):

A.K. Sater ◽

J.M. Alderton ◽

R.A. Steinhardt

Keyword(s):

Intracellular Ph ◽

Marginal Zone ◽

Phorbol Esters ◽

Regulation Of Gene Expression ◽

Homeobox Gene ◽

Neural Induction ◽

Ph Indicator ◽

Pharmacological Agents ◽

Dorsal Ectoderm ◽

Intracellular Alkalinization

In this paper, we show that an intracellular alkalinization of the dorsal ectoderm cells is among the earliest responses to neural induction in Xenopus. Planar explants of the dorsal marginal zone were prepared from embryos that had been microinjected during cleavage stages with the fluorescent pH indicator bis-carboxyethyl-carboxyfluorescein-dextran (BCECF-dextran), and intracellular pH (pHi) was monitored continuously by emission ratio microfluorimetry. During stage 10.5, the dorsal ectoderm cells undergo a sustained intracellular alkalinization of approximately 0.1 pH units in response to neural induction; in the absence of the inductive signal, the pH of the dorsal ectoderm cells decreases slightly. Ectoderm cells within planar explants of the ventral marginal zone show little change in pH during a similar period. This increase in intracellular pH is inhibited by 4, 4′-dihydrodiisothiocyanatostilbene-2, 2′-disulfonate (H2DIDS) or a low Na+/high Cl- medium, treatments that presumably affect anion transport. Under these conditions, expression of the anterior neural-specific homeobox gene engrailed is not detected, while the notochord-specific epitope recognized by the Tor-70 antibody is expressed in the presence of H2DIDS. This characteristic alkalinization is not evoked by pharmacological agents that reportedly alter ectodermal developmental pathways in Xenopus embryos, such as NH4Cl, phorbol esters, or cAMP-dependent protein kinase agonists. Our results suggest that an ionic regulatory event may participate in the regulation of gene expression in response to neural induction.

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Nitric Oxide Potentiates cAMP-Gated Cation Current by Intracellular Acidification in Feeding Neurons of Pleurobranchaea

Journal of Neurophysiology ◽

10.1152/jn.00021.2010 ◽

2010 ◽

Vol 104 (2) ◽

pp. 742-745 ◽

Cited By ~ 5

Author(s):

Kurt Potgieter ◽

Nathan G. Hatcher ◽

Rhanor Gillette ◽

Catherine R. McCrohan

Keyword(s):

Nitric Oxide ◽

Signaling Pathways ◽

Intracellular Ph ◽

Camp Signaling ◽

Intracellular Acidification ◽

Ph Indicator ◽

Intracellular Injection ◽

Cation Current ◽

Motor Network ◽

Important Regulator

A pH-sensitive cAMP-gated cation current ( INa,cAMP) is widely distributed in neurons of the feeding motor networks of gastropods. In the sea slug Pleurobranchaea this current is potentiated by nitric oxide (NO), which itself is produced by many feeding neurons. The action of NO is not dependent on either cGMP or cAMP signaling pathways. However, we found that NO potentiation of INa,cAMP in the serotonergic metacerebral cells could be blocked by intracellular injection of MOPS buffer (pH 7.2). In neurons injected with the pH indicator BCECF, NO induced rapid intracellular acidification to several tenths of a pH unit. Intracellular pH has not previously been identified as a specific target of NO, but in this system NO modulation of INa,cAMP via pHi may be an important regulator of the excitability of the feeding motor network.

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The chloride channel Bestrophin‐1 acts in the Malpighian tubule and hindgut of Drosophila melanogaster to maintain salt and water balance

The FASEB Journal ◽

10.1096/fasebj.2020.34.s1.05504 ◽

2020 ◽

Vol 34 (S1) ◽

pp. 1-1

Author(s):

Aylin Rodan ◽

John Pleinis ◽

Sima Jonusaite ◽

Jacob Hudac ◽

Austin Goodwin ◽

...

Keyword(s):

Drosophila Melanogaster ◽

Water Balance ◽

Chloride Channel ◽

Malpighian Tubule ◽

Salt And Water Balance

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Molecular characterization of the Drosophila melanogaster urate oxidase gene, an ecdysone-repressible gene expressed only in the malpighian tubules

Molecular and Cellular Biology ◽

10.1128/mcb.10.10.5114-5127.1990 ◽

1990 ◽

Vol 10 (10) ◽

pp. 5114-5127

Author(s):

L L Wallrath ◽

J B Burnett ◽

T B Friedman

Keyword(s):

Drosophila Melanogaster ◽

Amino Acid ◽

Regulatory Element ◽

Malpighian Tubule ◽

Amino Acid Sequences ◽

Malpighian Tubules ◽

P Element ◽

Urate Oxidase ◽

Base Pairs ◽

Oxidase Gene

The urate oxidase (UO) gene of Drosophila melanogaster is expressed during the third-instar larval and adult stages, exclusively within a subset of cells of the Malpighian tubules. The UO gene contains a 69-base-pair intron and encodes mature mRNAs of 1,224, 1,227, and 1,244 nucleotides, depending on the site of 3' endonucleolytic cleavage prior to polyadenylation. A direct repeat, 5'-AAGTGAGAGTGAT-3', is the proposed cis-regulatory element involved in 20-hydroxyecdysone repression of the UO gene. The deduced amino acid sequences of UO of D. melanogaster, rat, mouse, and pig and uricase II of soybean show 32 to 38% identity, with 22% of amino acid residues identical in all species. With use of P-element-mediated germ line transformation, 826 base pairs 5' and approximately 1,200 base pairs 3' of the D. melanogaster UO transcribed region contain all of the cis elements allowing for appropriate temporal regulation and Malpighian tubule-specific expression of the UO gene.

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