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.

AQP-2

DEFINITION:

Aquaporin-2.

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).

regulated

DEFINITION:

1. Having been adjusted to a certain standard.

2. In biology, describing the adaptation of form or behavior of an organism to changed conditions.

water channel

DEFINITION:

A channel in the plasma membrane of plant and animal cells that permits passage of water molecules; chemical substances such as vasopressin cause the opening of new channels and increase permeability.

renal collecting duct

DEFINITION:

Also known as the tubulus renalis colligens, or renal collecting tubule: That structure of the kidney consisting of the arcuate renal tubule, straight collecting tubule, and papillary duct considered together.

urine

DEFINITION:

The fluid excreted by the kidneys, passed through the ureters, stored in the bladder, and discharged through the urethra. Urine, in health, has an amber color, a slight acid reaction, a peculiar odor, and a bitter, saline taste.

urinary excretion

DEFINITION:

The throwing off or elimination of urine by normal discharge.

AQP-2

DEFINITION:

Aquaporin-2.

radioimmunoassay

DEFINITION:

A highly sensitive and specific assay method that uses the competition between radiolabeled and unlabeled substances in an antigen-antibody reaction to determine the concentration of the unlabeled substance; it can be used to determine antibody concentrations or to determine the concentration of any substance against which specific antibody can be produced. Abbreviated RIA.

preterm

DEFINITION:

That which occurs prior to a definite period or specified time of duration, such as the premature culmination of pregnancy at less than 40 weeks from the last menstrual period or 38 weeks from conception.

AQP-2

DEFINITION:

Aquaporin-2.

correlated

DEFINITION:

See correlation.

urine osmolality

DEFINITION:

The concentration of osmotically active particles in solution (in this case, urine) expressed in terms of osmoles of solute per kilogram of solvent. The osmolality is directly proportional to the colligative properties of solutions: osmotic pressure, boiling point elevation, freezing point depression, and vapor pressure lowering.

preterm

DEFINITION:

That which occurs prior to a definite period or specified time of duration, such as the premature culmination of pregnancy at less than 40 weeks from the last menstrual period or 38 weeks from conception.

AQP-2 water channels

DEFINITION:

One of a family of membrane channel proteins that serve as selective pores through which water crosses the plasma membranes of many human tissues and cell types.

expressed

DEFINITION:

1. Showing a detectable effect of a gene.

2. Made known; shown.

3. Squeezed out; extracted by pressing.

renal collecting duct

DEFINITION:

Also known as the tubulus renalis colligens, or renal collecting tubule: That structure of the kidney consisting of the arcuate renal tubule, straight collecting tubule, and papillary duct considered together.

preterm

DEFINITION:

That which occurs prior to a definite period or specified time of duration, such as the premature culmination of pregnancy at less than 40 weeks from the last menstrual period or 38 weeks from conception.