WordNet

(of a solution) the extent to which a solution has a higher osmotic pressure than some other
(of living tissue) in a state of abnormally high tension; "hypertonic muscle tissue"
(of a solution) having a higher osmotic pressure than a comparison solution

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/12/03 15:29:54」(JST)

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"Hypotonic" redirects here. For the muscular disease, see Hypotonia.

Effect of different solutions on blood cells

Micrographs of osmotic pressure on red blood cells

Tonicity is a measure of the osmotic pressure gradient (as defined by the water potential of the two solutions) of two solutions separated by a semipermeable membrane. It is commonly used when describing the response of cells immersed in an external solution. Like osmotic pressure, tonicity is influenced only by solutes that cannot cross the membrane, as only these exert an osmotic pressure. Solutes able to freely cross the membrane do not affect tonicity because they will always be in equal concentrations on both sides of the membrane.

There are three classifications of tonicity that one solution can have relative to another. The three are hypertonic, hypotonic, and isotonic.^[1]

Hypertonicity

Hypertonic refers to a greater concentration. In biology, a hypertonic solution is one with a higher concentration of solutes on the outside of the cell. When a cell is immersed into a hypertonic solution, the tendency is for water to want to flow out of the cell in order to balance the concentration of the solutes.

However, a hypertonic cell has a higher concentration of solutes than the surrounding solution, causing water to rush into the cell in an effort to balance out the concentration of solutes. The affinity of water wanting to rush in can be quantified as the osmotic pressure.^[2]

Hypotonicity

Hypotonic refers to a lesser concentration. A hypotonic cell has a lower concentration of solutes than its surroundings, so in an attempt to balance concentrations, water will rush out of the cell, causing crenation. The cell becomes wrinkled and distorted.^[3]

When plant cells are hypotonic, the flexible cell membrane pulls away from the rigid cell wall, but remains joined to the cell wall at points called plasmodesmata. The cell takes on the appearance of a pincushion, and the plasmodesmata almost cease to function because they become constricted: a condition known as plasmolysis. In plant cells the terms isotonic, hypotonic and hypertonic cannot strictly be used accurately because the pressure exerted by the cell wall significantly affects the osmotic equilibrium point.

Some organisms have evolved intricate methods of circumventing hypotonicity. For example, saltwater is hypertonic to the fish that live in it. They need a large surface area in their gills in contact with seawater for gas exchange, thus they lose water osmotically to the sea from gill cells. They respond to the loss by drinking large amounts of saltwater, and actively excreting the excess salt. This process is called osmoregulation.

A hypertonic solution is used in osmotherapy to treat cerebral hemorrhage.^{[citation needed]}

Isotonicity

An isotonic solution is one in which its effective osmole concentration is the same as the solute concentration of another solution with which it is compared. This occurs, for example, when the concentration of both water and total solute molecules are the same in an external solution as in the cell content. Water molecules diffuse through the plasma membrane in both directions, and as the rate of water diffusion is the same in both direction that cell will neither gain nor lose water.

References

^ Sperelakis, Nicholas (2011). Cell Physiology Source Book: Essentials of Membrane Biophysics. Academic Press. pp. 288. ISBN 978-0-12-387738-3.
^ Brandis, Kerry. "Fluid Physiology". http://www.anaesthesiamcq.com/FluidBook/fl2_3.php. Retrieved 11/22/2012.
^ "Definition — hypotonic". The Free Dictionary. http://medical-dictionary.thefreedictionary.com/hypotonic. Retrieved 23 August 2012.

UpToDate Contents

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English Journal

Muscle histopathology in children with spastic cerebral palsy receiving botulinum toxin type A.

Valentine J1,2, Stannage K3, Fabian V4, Ellis K4, Reid S5, Pitcher C5, Elliott C1,6.
Muscle & nerve.Muscle Nerve.2016 Mar;53(3):407-14. doi: 10.1002/mus.24763. Epub 2016 Jan 5.
INTRODUCTION: Botulinum toxin A (BoNTA) is routine treatment for hypertonicity in children with cerebral palsy (CP).METHODS: This single-blind, prospective, cross-sectional study of 10 participants (mean age 11 years 7 months) was done to determine the relationship between muscle histopathology and
PMID 26154631

Fractional anisotropy in children with dystonia or spasticity correlates with the selection for DBS or ITB movement disorder surgery.

Lumsden DE1,2, Ashmore J3, Ball G4, Charles-Edwards G3,5, Selway R6, Ashkan K6,7, Lin JP8.
Neuroradiology.Neuroradiology.2016 Jan 12. [Epub ahead of print]
INTRODUCTION: There is increasing interest in neurosurgical interventions for hypertonicity in children and young people (CAYP), which often presents with a mixture of dystonia and spasticity. Significant spasticity would usually be considered a contraindication for deep brain stimulation (DBS) and
PMID 26759316

Peptide affinity analysis of proteins that bind to an unstructured n-terminal region of the osmoprotective transcription factor NFAT5.

DuMond JF1, Ramkissoon K1, Zhang X1, Izumi Y2, Wang X1, Eguchi K2, Gao S1, Mukoyama M2, Burg MB3, Ferraris JD1.
Physiological genomics.Physiol Genomics.2016 Jan 12:physiolgenomics.00110.2015. doi: 10.1152/physiolgenomics.00110.2015. [Epub ahead of print]
NFAT5 is an osmoregulated transcription factor that particularly increases expression of genes involved in protection against hypertonicity. Transcription factors often contain unstructured regions that bind co-regulatory proteins that are crucial for their function. The n-terminal region of NFAT5 c
PMID 26757802

Japanese Journal

味覚情報処理におけるタイトジャンクションと浸透圧の役割

生物物理 54(6), 303-306, 2014
NAID 130004713029

TRPM4 Channels Mediate Hypertonicity-induced, Ca²⁺-impermeable, Non-selective Cation Currents in a Cervical Cancer Cell Line, HeLa Cells

信州医学雑誌 62(1), 33-44, 2014
NAID 130004551913

長期経管栄養施行中の重症心身障害児(者)の腸内菌叢および糞便性状の検討

腸内細菌学雑誌 = Journal of intestinal microbiology 27(1), 1-6, 2013-01-01
NAID 10031141107

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