Hypotonicity induced K+ and anion conductive pathways activation in eel intestinal epithelium

Lionetto, Maria Giulia; Giordano, Maria Elena; Nuccio, Francesco De; Nicolardi, Giuseppe; Hoffmann, Else K.; Schettino, T.

doi:10.1242/jeb.01440

Cited by 28 publications

(36 citation statements)

References 66 publications

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“…As previously demonstrated [44] the eel intestinal epithelium responded to a hypotonic challenge with a Ca 2+ -dependent biphasic decrease in V te and Isc (Fig. 6, control trace) which is correlated with a regulatory volume decrease (RVD) response.…”

Section: Role Of Bk Channels In Rvdsupporting

confidence: 72%

“…As previously demonstrated [42,43] this epithelium is sensitive to the osmolarity of the extracellular medium and shows a dynamic regulation of cell volume with a RVD response after hypotonic stress, making this tissue a good physiological model for epithelial cell volume regulation research. As previously demonstrated by short circuit current measurements [44] hypotonicity induces a Ca 2+ -dependent biphasic decrease of V te and Isc, that was attributed to the hypotonicity induced activation of several ion channels including iberiotoxin-sensitive K + channels [44]. In the present paper using rat BK channel-specific primer, a RT-PCR signal of 696 pb cDNA was detected in eel intestine, whole nucleotide sequence showed high similarity (83%) to the alpha subunit of BK channel fam- ily.…”

Section: +supporting

confidence: 60%

“…Morphometric analysis of the epithelium height was performed as previously described [44]. Briefly, small segments of the eel middle intestine, stripped from their outer layers, perfused with Ringer solution (315 mOsm), were fixed before (control), after 5 min and after 45 min exposure to hyposmotic Ringer solution (160 mOsm) respectively and embedded in Epon 812.…”

Section: Tissue Morphometric Analysismentioning

confidence: 99%

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Molecular and Functional Expression of High Conductance Ca2+ Activated K+ Channels in the Eel Intestinal Epithelium

Lionetto

Rizzello²,

Giordano³

et al. 2008

Cell Physiol Biochem

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Several types of K⁺ channels have been identified in epithelial cells. Among them high conductance Ca²⁺-activated K⁺ channels (BK channels) are of relevant importance for their involvement in regulatory volume decrease (RVD) response following hypotonic stress. The aim of the present work was to investigate the functional and molecular expression of BK in the eel intestine, which is a useful experimental model for cell volume regulation research. In the present paper using rat BK channel-specific primer, a RT-PCR signal of 696 pb cDNA was detected in eel intestine, whole nucleotide sequence showed high similarity (83%) to the alpha subunit of BK channel family. BK channel protein expression was verified by immunoblotting and confocal microscopy, while the functional role of BK channels in epithelial ion transport mechanisms and cell volume regulation was examined by electrophysiological and morphometric analysis on the intact tissue. BK_Ca channels appeared to be localized along all the plasma membrane of the enterocytes; the apical part of the villi showed the most intense immunostaining. These channels were silent in basal condition, but were activated on both membranes (apical and basolateral) by increasing intracellular Ca²⁺ concentration with the Ca²⁺ ionophore ionomycin (1µM). BK_Ca channels were also activated on both membranes by hypotonic swelling of the epithelium and their inhibition by 100 nM iberiotoxin (specific BK_Ca inhibitor) abolished the Regulatory Volume Decrease (RVD) of the intestinal cells after hypotonic swelling. In conclusion, our results demonstrated the molecular and functional expression of high conductance Ca²⁺ -activated K⁺ channels in eel intestine; the physiological role of these channels is mainly related to the RVD response of the epithelial cells following hypotonic swelling.

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Section: Role Of Bk Channels In Rvdsupporting

confidence: 72%

Section: +supporting

confidence: 60%

Section: Tissue Morphometric Analysismentioning

confidence: 99%

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Molecular and Functional Expression of High Conductance Ca2+ Activated K+ Channels in the Eel Intestinal Epithelium

Lionetto

Rizzello²,

Giordano³

et al. 2008

Cell Physiol Biochem

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“…The Na ϩ -K ϩ -ATPase on the basolateral membrane provides the driving force for NKCC2, a model similar to that proposed for the mammalian cTAL. It has been shown that swelling-activated K ϩ and anion-conductive pathways are important in the response to hypotonicity in the eel intestine (572), and that conversely, shrinkage activation of NKCC2 plays a central role in the response to hypertonicity (573; see Refs. 368, 575; see also sect.…”

Section: Osmotic Regulation Of Salt Transportmentioning

confidence: 99%

Physiology of Cell Volume Regulation in Vertebrates

Hoffmann

Lambert²,

Pedersen³

2009

Physiological Reviews

1,302

1,677

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The ability to control cell volume is pivotal for cell function. Cell volume perturbation elicits a wide array of signaling events, leading to protective (e.g., cytoskeletal rearrangement) and adaptive (e.g., altered expression of osmolyte transporters and heat shock proteins) measures and, in most cases, activation of volume regulatory osmolyte transport. After acute swelling, cell volume is regulated by the process of regulatory volume decrease (RVD), which involves the activation of KCl cotransport and of channels mediating K+, Cl−, and taurine efflux. Conversely, after acute shrinkage, cell volume is regulated by the process of regulatory volume increase (RVI), which is mediated primarily by Na+/H+exchange, Na+-K+-2Cl−cotransport, and Na+channels. Here, we review in detail the current knowledge regarding the molecular identity of these transport pathways and their regulation by, e.g., membrane deformation, ionic strength, Ca2+, protein kinases and phosphatases, cytoskeletal elements, GTP binding proteins, lipid mediators, and reactive oxygen species, upon changes in cell volume. We also discuss the nature of the upstream elements in volume sensing in vertebrate organisms. Importantly, cell volume impacts on a wide array of physiological processes, including transepithelial transport; cell migration, proliferation, and death; and changes in cell volume function as specific signals regulating these processes. A discussion of this issue concludes the review.

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“…The cell volume regulation mechanisms are highly conserved and principally similar in cells from various tissues as well as between evolutionary distant species [22,23,24,25,26,27]. Following a hypotonic cell swelling, they consist in the release of osmolytes, mainly K + and Cl - , followed by loss of osmotically obliged water and are termed Regulatory Volume Decrease (RVD); following a hypertonic shrinkage they consist in the uptake of osmolytes followed by gain of osmotically obliged water and are termed Regulatory Volume Increase (RVI) [28,27].…”

Section: Introductionmentioning

confidence: 99%

Cell Volume Regulation and Apoptotic Volume Decrease in Rat Distal Colon Superficial Enterocytes

Antico

Lionetto

Giordano

et al. 2013

Cell Physiol Biochem

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Background: The colon epithelium is physiologically exposed to osmotic stress, and the activation of cell volume regulation mechanisms is essential in colonocyte physiology. Moreover, colon is characterized by a high apoptotic rate of mature cells balancing the high division rate of stem cells. Aim: The aim of the present work was to investigate the main cell volume regulation mechanisms in rat colon surface colonocytes and their role in apoptosis. Methods: Cell volume changes were measured by light microscopy and video imaging on colon explants; apoptosis sign appearance was monitored by confocal microscopy on annexin V/propidium iodide labeled explants. Results: Superficial colonocytes showed a dynamic regulation of their cell volume during anisosmotic conditions with a Regulatory Volume Increase (RVI) response following hypertonic shrinkage and Regulatory Volume Decrease (RVD) response following hypotonic swelling. RVI was completely inhibited by bumetanide, while RVD was completely abolished by high K⁺ or iberiotoxin treatment and by extracellular Ca²⁺ removal. DIDS incubation was also able to affect the RVD response. When colon explants were exposed to H₂O₂ as apoptotic inducer, colonocytes underwent an isotonic volume decrease ascribable to Apoptotic Volume Decrease (AVD) within about four hours of exposure. AVD was shown to precede annexin V positivity. It was also inhibited by high K⁺ or iberiotoxin treatment. Interestingly, treatment with iberiotoxin significantly inhibited apoptosis progression. Conclusions: In rat superficial colonocytes K⁺ efflux through high conductance Ca²⁺-activated K⁺ channels (BK channels) was demonstrated to be the main mechanism of RVD and to plays also a crucial role in the AVD process and in the progression of apoptosis.

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Hypotonicity induced K+ and anion conductive pathways activation in eel intestinal epithelium

Abstract: The electrophysiological response to hypotonic stress was completely abolished by Ca 2+ removal from the Ringer perfusing solution, but was not affected by depletion of intracellular Ca 2+ stores by thapsigargin.

Cited by 28 publications

References 66 publications

Molecular and Functional Expression of High Conductance Ca<sup>2+</sup> Activated K<sup>+</sup> Channels in the Eel Intestinal Epithelium

Molecular and Functional Expression of High Conductance Ca<sup>2+</sup> Activated K<sup>+</sup> Channels in the Eel Intestinal Epithelium

Physiology of Cell Volume Regulation in Vertebrates

Cell Volume Regulation and Apoptotic Volume Decrease in Rat Distal Colon Superficial Enterocytes

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Hypotonicity induced K+ and anion conductive pathways activation in eel intestinal epithelium

Abstract: The electrophysiological response to hypotonic stress was completely abolished by Ca 2+ removal from the Ringer perfusing solution, but was not affected by depletion of intracellular Ca 2+ stores by thapsigargin.

Cited by 28 publications

References 66 publications

Molecular and Functional Expression of High Conductance Ca<sup>2&plus;</sup> Activated K<sup>&plus;</sup> Channels in the Eel Intestinal Epithelium

Molecular and Functional Expression of High Conductance Ca<sup>2&plus;</sup> Activated K<sup>&plus;</sup> Channels in the Eel Intestinal Epithelium

Physiology of Cell Volume Regulation in Vertebrates

Cell Volume Regulation and Apoptotic Volume Decrease in Rat Distal Colon Superficial Enterocytes

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Product

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Molecular and Functional Expression of High Conductance Ca<sup>2+</sup> Activated K<sup>+</sup> Channels in the Eel Intestinal Epithelium

Molecular and Functional Expression of High Conductance Ca<sup>2+</sup> Activated K<sup>+</sup> Channels in the Eel Intestinal Epithelium