polyuria

DEFINITION:

The passage of a large volume of urine in a given period, a characteristic of diabetes.

osmolality

DEFINITION:

The concentration of an osmotic solution especially when measured in osmols or milliosmols per 1000 grams of solvent.
Osmolality is a measure of the concentration of particles in a solution. A highly concentrated solution will have a high osmolality. That is, it will have more particles per unit of solvent than a solution with a low osmolality. (JC)

vasopressin V(2) receptor

DEFINITION:

The molecular structure within a cell or on the surface to which the antidiuretic hormone, arginine vasopressin, binds.

mRNA

DEFINITION:

Messenger RNA. RNA molecules, usually 400 to 10,000 bases long, that serve as templates for protein synthesis (translation); in eukaryotes they have characteristic posttranscriptional modifications, the 5'-cap and poly A tail. The base sequence of an mRNA transcript completely specifies the corresponding polypeptide amino acid sequence.

binding

DEFINITION:

1. Wrapping with a binder or bandage.

2. Forming a weak, reversible chemical bond, e.g., antigen to antibody or hormone to receptor.

membrane

DEFINITION:

A thin layer of tissue which covers a surface, lines a cavity, or divides a space or organ.

apical membrane - Pertaining to or located at the apex.

basolateral membrane - Pertaining to the base and sides.

plasma membrane - The structure enveloping a cell, enclosing the cytoplasm, and forming a selective permeability barrier; it consists of lipids, proteins, and some carbohydrates, the lipids thought to form a bilayer in which integral proteins are embedded to varying degrees.

postsynaptic membrane - The area of plasma membrane of a postsynaptic cell, either a muscle fiber or a neuron, that is within the synapse and has areas especially adapted for receiving neurotransmitters.

presynaptic membrane - Area of the plasma membrane of a presynaptic axon that is within the synapse and has sites (active zones) especially adapted for the release of neurotransmitters.

semipermeable membrane - A membrane that permits the passage of a solvent, such as water, but prevents the passage of the dissolved substance, or solute.

cAMP

DEFINITION:

Cyclic AMP (cyclic adenosine monophosphate).

expression

DEFINITION:

1. The aspect or appearance of the face (or surface of a cell) as determined by the physical or emotional state.

2. The act of squeezing or evacuating by pressure; a term used in pharmacy, surgery, and obstetrics.

3. The detectable effect of a gene.

4. A representation of value, relation, or the like (e.g., ratio).

aquaporin-1

DEFINITION:

Also known as CHIP-28, aquaporin-1 is the major water channel of the red blood cells. In the kidneys, it is involved in the reabsorption of most of the waste filtered through the glomerula.

AQP1

DEFINITION:

Aquaporin-1.

aquaporin-2

DEFINITION:

Also called WCH-CD, this water channel makes the principal cells of the inner medullary collecting duct in the kidneys more permeable to water. Lack of functional aquaporin-2 gene leads to a rare form of nephrogenic diabetes insipidus.

AQP2

DEFINITION:

Aquaporin-2.

AQP3

DEFINITION:

Aquaporin-3.

expression

DEFINITION:

1. The aspect or appearance of the face (or surface of a cell) as determined by the physical or emotional state.

2. The act of squeezing or evacuating by pressure; a term used in pharmacy, surgery, and obstetrics.

3. The detectable effect of a gene.

4. A representation of value, relation, or the like (e.g., ratio).

AQP2

DEFINITION:

Aquaporin-2.

intracellular

DEFINITION:

Situated or occurring within a cell or cells.

inner medulla

DEFINITION:

Inner medulla of kidney: inner zone of renal medulla.

renal cortex

DEFINITION:

Kidney cortex (cortex renalis). The outer part of the substance of the kidney, composed mainly of glomeruli and convoluted tubules.

polyuria

DEFINITION:

The passage of a large volume of urine in a given period, a characteristic of diabetes.

downregulation

DEFINITION:

A decrease in the number of receptors for a chemical or drug on cell surfaces in a given area, usually due to long-term exposure to the agent. (Dorland's Illustrated Medical Dictionary, 29th edition)

Downregulation of aquaporin 2: The number of aquaporin 2 water channels will be decreased, i.e., regulated to a lower number of channels expressed on the luminal membrane (D. Bichet).

Downregulation of AQP2 means that there are many conditions with acquired nephrogenic diabetes insipidus (vasopressin-resistent polyuria) which result in a reduction in the levels of AQP2 protein in the collecting duct cells. Since AQP2 is essential for reabsorption of water from the collecting duct lumen back to the circulation, the absence or reduced levels of AQP2 (downregulation) results in the development of polyuria. Thus the conditions associated with this downregulation of AQP2 share many common features with the inherited forms of NDI (with mutations in vasopressin V2 receptor) since this condition is also associated with a reduced/absence of regulation of AQP2. This regulation is important for keeping the levels of AQP2 protein up, but it is also extremely important in regulating the trafficking of AQP2 from the reservoir in small vesicles to the apical plasma membrane (its active site for water reabsorption—the site where the water channel faces the water to be reabsorbed). This is why the studies of the very common acquired forms of NDI are very important in connection with inherited NDI (the shared elements of regulation or rather dysregulation) (S. Nielsen).

AQP2

DEFINITION:

Aquaporin-2.

AQP3

DEFINITION:

Aquaporin-3.

expression

DEFINITION:

1. The aspect or appearance of the face (or surface of a cell) as determined by the physical or emotional state.

2. The act of squeezing or evacuating by pressure; a term used in pharmacy, surgery, and obstetrics.

3. The detectable effect of a gene.

4. A representation of value, relation, or the like (e.g., ratio).

medullary collecting duct

DEFINITION:

The distal part of the renal tubule, including the loop of Henle, lying within the medulla. See also duct .

vasopressin

DEFINITION:

1. One of two octapeptide hormones formed by the neuronal cells of the hypothalamic nuclei and stored in the posterior lobe of the pituitary gland (neurohypophysis), the other being oxytocin. It stimulates the contraction of the muscular tissue of the capillaries and arterioles, raising the blood pressure. It promotes contraction of the intestinal musculature and increases peristalsis, and also exerts some contractile influence on the uterus. It also has a specific effect on the epithelial cells of the distal portion of the uriniferous tubule, augmenting resorption of water independently of solutes, resulting in concentration of urine and dilution of blood serum. Its rate of secretion is regulated chiefly by the osmolarity of the plasma.

2. [USP], A pharmaceutical preparation of the same principle, prepared synthetically or obtained from the posterior pituitary of healthy domestic animals used for food by man; used mainly as an antidiuretic in the treatment of acute or chronic diabetes insipidus, administered intramuscularly as a test of hypothalamo-neurohypophysial-renal function in distinguishing central from nephrogenic diabetes insipidus; it may also be used to stimulate smooth muscle tissue, especially to induce vasoconstriction in the presence of hemorrhage. Called also antidiuretic hormone (ADH).

mediated

DEFINITION:

Accomplished by the aid of an intervening medium.

cAMP

DEFINITION:

Cyclic AMP (cyclic adenosine monophosphate).

permission

DEFINITION:

Formal consent; authorization.