slow-reacting substance

Also found in: Dictionary, Thesaurus, Legal, Acronyms, Encyclopedia.
Related to slow-reacting substance: SRSA, PAF, ECF-A

slow-·re·act·ing sub·stance (SRS),

, slow-reacting substance of anaphylaxisSRS-A
a lipoprotein of low molecular weight composed of leukotrienes; it is released in anaphylactic shock and produces slower and more prolonged contraction of muscle than histamine does; it is active in the presence of antihistamines (but not epinephrine) and is newly generated after unpreformed mast cell generation; it induces the effect observed in anaphylactic reactions. Compare: peptidyl leukotrienes.
Farlex Partner Medical Dictionary © Farlex 2012


(sub'stans) [L. substantia]
1. Material; matter.
2. Substantia.
3. A chemical or drug.
4. When used in a medicolegal context, a chemical with potential for abuse. A great variety of entities are included: alcohol, nicotine, caffeine, sedatives, hypnotics, anxiolytics, and illicit drugs such as cannabis, heroin, or methamphetamines. Almost any substance may be abused even though its clinical use is approved when used as prescribed.

anterior perforated substance

The portion of the rhinencephalon lying immediately anterior to the optic chiasm. It is perforated by numerous small arteries.

black substance

Substantia nigra.

chromophilic substance

A substance found in the cytoplasm of certain cells that stains similar to chromatin with basic dyes. It includes Nissl bodies of neurons and granules in serozymogenic cells.

colloid substance

Jelly-like substance in colloid degeneration.

gray substance

An outdated term for the gray matter of the central nervous system.

ground substance

The matrix or intercellular substance in which the cells of an organ or tissue are embedded.

high threshold substance

A substance such as glucose or sodium chloride present in the blood and excreted by the kidney only when its concentration exceeds a certain level.

ketogenic substance

A substance that, in its metabolism, gives rise to ketone bodies.

low threshold substance

A substance such as urea or uric acid that is excreted by the kidney from the blood almost in its entirety. It occurs in the urine in high concentrations.

medullary substance

An obsolete term for the inner part of an organ such as a bone.

Nissl substance

See: Nissl, Franz

posterior perforated substance

A triangular area forming the floor of the interpeduncular fossa. It lies immediately behind the corpora mammillaria and contains numerous openings for blood vessels.

pressor substance

A substance that elevates arterial blood pressure.

reticular substance

The skein of threads present in some red blood cells. These are visible only when the cells are appropriately stained.

slow-reacting substance

See: slow-reacting substance of anaphylaxis
Medical Dictionary, © 2009 Farlex and Partners