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Ouabain-induced cytoplasmic vesicles and their role in cell volume maintenance.

Russo MA, Morgante E, Russo A, van Rossum GD, Tafani M - Biomed Res Int (2015)

Bottom Line: Na(+)/K(+)-pump may be blocked by ouabain, a digitalic derivative, by inhibition of ATP, or by drastic ion alterations of extracellular fluid.In particular, hepatocytes were able to sequester ions and water in intracellular vesicles and then secrete them at the bile canaliculus pole.This review summarizes evidences regarding this mechanism, problems that are still pending, and questions that need to be answered.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular and Cellular Pathology, IRCCS San Raffaele Pisana, Via di Val Cannuta 247, 00166 Roma, Italy.

ABSTRACT
Cellular swelling is controlled by an active mechanism of cell volume regulation driven by a Na(+)/K(+)-dependent ATPase and by aquaporins which translocate water along the osmotic gradient. Na(+)/K(+)-pump may be blocked by ouabain, a digitalic derivative, by inhibition of ATP, or by drastic ion alterations of extracellular fluid. However, it has been observed that some tissues are still able to control their volume despite the presence of ouabain, suggesting the existence of other mechanisms of cell volume control. In 1977, by correlating electron microscopy observation with ion and water composition of liver slices incubated in different metabolic conditions in the presence or absence of ouabain, we observed that hepatocytes were able to control their volume extruding water and recovering ion composition in the presence of ouabain. In particular, hepatocytes were able to sequester ions and water in intracellular vesicles and then secrete them at the bile canaliculus pole. We named this "vesicular mechanism of cell volume control." Afterward, this mechanism has been confirmed by us and other laboratories in several mammalian tissues. This review summarizes evidences regarding this mechanism, problems that are still pending, and questions that need to be answered. Finally, we shortly review the importance of cell volume control in some human pathological conditions.

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Related in: MedlinePlus

Liver slices were incubated for 90 min at 1°C followed by 60 min at 38°C, with 10 μM phalloidin plus 2 mM ouabain [7]. (a) This micrograph shows an increase in the size and number of vesicles. These show a rather irregular outline probably resulting from the fusion of smaller vesicles. The vesicular contents are clear and similar to that seen with ouabain alone. (b) Detail of a very large vesicle close to a small bile canaliculus. (c) Detail of homogeneous submembrane zone typical of the stabilization effect of phalloidin on cortical actin. BC = bile canaliculus; V = vesicles; S = sinusoid.
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fig8: Liver slices were incubated for 90 min at 1°C followed by 60 min at 38°C, with 10 μM phalloidin plus 2 mM ouabain [7]. (a) This micrograph shows an increase in the size and number of vesicles. These show a rather irregular outline probably resulting from the fusion of smaller vesicles. The vesicular contents are clear and similar to that seen with ouabain alone. (b) Detail of a very large vesicle close to a small bile canaliculus. (c) Detail of homogeneous submembrane zone typical of the stabilization effect of phalloidin on cortical actin. BC = bile canaliculus; V = vesicles; S = sinusoid.

Mentions: In the presence of ouabain, results with phalloidin and cytochalasins A, D, and E were all rather similar to the observations previously obtained with cytochalasin B alone [24]. All these agents inhibited the ouabain-resistant extrusion of total tissue water to varying degrees and caused an increase in the number, size, and area of distribution beyond that seen with ouabain alone (Figures 6, 7, and 8) [7]. Furthermore, the vesicles typically lacked the orientation towards the Golgi and excretory pole as seen with ouabain alone (Figures 6(a) and 8(a)). This distribution suggests that the vesicles are formed but are unable to move on their normal path and to extrude their content at the canalicular pole. The reduced extrusion of total and intracellular water was, in each case, associated with an approximately equimolar reduction of the extrusions of Na+ and Cl−.


Ouabain-induced cytoplasmic vesicles and their role in cell volume maintenance.

Russo MA, Morgante E, Russo A, van Rossum GD, Tafani M - Biomed Res Int (2015)

Liver slices were incubated for 90 min at 1°C followed by 60 min at 38°C, with 10 μM phalloidin plus 2 mM ouabain [7]. (a) This micrograph shows an increase in the size and number of vesicles. These show a rather irregular outline probably resulting from the fusion of smaller vesicles. The vesicular contents are clear and similar to that seen with ouabain alone. (b) Detail of a very large vesicle close to a small bile canaliculus. (c) Detail of homogeneous submembrane zone typical of the stabilization effect of phalloidin on cortical actin. BC = bile canaliculus; V = vesicles; S = sinusoid.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383472&req=5

fig8: Liver slices were incubated for 90 min at 1°C followed by 60 min at 38°C, with 10 μM phalloidin plus 2 mM ouabain [7]. (a) This micrograph shows an increase in the size and number of vesicles. These show a rather irregular outline probably resulting from the fusion of smaller vesicles. The vesicular contents are clear and similar to that seen with ouabain alone. (b) Detail of a very large vesicle close to a small bile canaliculus. (c) Detail of homogeneous submembrane zone typical of the stabilization effect of phalloidin on cortical actin. BC = bile canaliculus; V = vesicles; S = sinusoid.
Mentions: In the presence of ouabain, results with phalloidin and cytochalasins A, D, and E were all rather similar to the observations previously obtained with cytochalasin B alone [24]. All these agents inhibited the ouabain-resistant extrusion of total tissue water to varying degrees and caused an increase in the number, size, and area of distribution beyond that seen with ouabain alone (Figures 6, 7, and 8) [7]. Furthermore, the vesicles typically lacked the orientation towards the Golgi and excretory pole as seen with ouabain alone (Figures 6(a) and 8(a)). This distribution suggests that the vesicles are formed but are unable to move on their normal path and to extrude their content at the canalicular pole. The reduced extrusion of total and intracellular water was, in each case, associated with an approximately equimolar reduction of the extrusions of Na+ and Cl−.

Bottom Line: Na(+)/K(+)-pump may be blocked by ouabain, a digitalic derivative, by inhibition of ATP, or by drastic ion alterations of extracellular fluid.In particular, hepatocytes were able to sequester ions and water in intracellular vesicles and then secrete them at the bile canaliculus pole.This review summarizes evidences regarding this mechanism, problems that are still pending, and questions that need to be answered.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular and Cellular Pathology, IRCCS San Raffaele Pisana, Via di Val Cannuta 247, 00166 Roma, Italy.

ABSTRACT
Cellular swelling is controlled by an active mechanism of cell volume regulation driven by a Na(+)/K(+)-dependent ATPase and by aquaporins which translocate water along the osmotic gradient. Na(+)/K(+)-pump may be blocked by ouabain, a digitalic derivative, by inhibition of ATP, or by drastic ion alterations of extracellular fluid. However, it has been observed that some tissues are still able to control their volume despite the presence of ouabain, suggesting the existence of other mechanisms of cell volume control. In 1977, by correlating electron microscopy observation with ion and water composition of liver slices incubated in different metabolic conditions in the presence or absence of ouabain, we observed that hepatocytes were able to control their volume extruding water and recovering ion composition in the presence of ouabain. In particular, hepatocytes were able to sequester ions and water in intracellular vesicles and then secrete them at the bile canaliculus pole. We named this "vesicular mechanism of cell volume control." Afterward, this mechanism has been confirmed by us and other laboratories in several mammalian tissues. This review summarizes evidences regarding this mechanism, problems that are still pending, and questions that need to be answered. Finally, we shortly review the importance of cell volume control in some human pathological conditions.

Show MeSH
Related in: MedlinePlus