Ryanodine is a poisonous

diterpenoid Diterpenes are a class of chemical compounds composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being ...

found in the South American plant ''

Ryania speciosa ''Ryania speciosa'' is a species of plant in the family Salicaceae. The species is significant partly because the ryanoid insecticides are derived from, and have the same mode of action as the alkaloid ryanodine, which was originally extracte ...

'' (

Salicaceae The Salicaceae is the willow family of flowering plants. The traditional family (Salicaceae ''sensu stricto'') included the willows, poplar, aspen, and cottonwoods. Genetic studies summarized by the Angiosperm Phylogeny Group (APG) have greatly ...

). It was originally used as an

insecticide Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...

. The compound has extremely high affinity to the open-form ryanodine receptor, a group of

calcium channel A calcium channel is an ion channel which shows selective permeability to calcium ions. It is sometimes synonymous with voltage-gated calcium channel, although there are also ligand-gated calcium channels. Comparison tables The following tables e ...

s found in

skeletal A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

muscle, smooth muscle, and

heart muscle Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle tha ...

cells. It binds with such high affinity to the receptor that it was used as a label for the first purification of that class of

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of io ...

s and gave its name to it. At

nanomolar Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular of a solute in a solution, in terms of amount of substance per unit volume of solut ...

concentrations, ryanodine locks the receptor in a half-open state, whereas it fully closes them at

micromolar Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular of a solute in a solution, in terms of amount of substance per unit volume of sol ...

concentration. The effect of the nanomolar-level binding is that ryanodine causes release of

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

from calcium stores as the

sarcoplasmic reticulum The sarcoplasmic reticulum (SR) is a membrane-bound structure found within muscle cells that is similar to the smooth endoplasmic reticulum in other Cell (biology), cells. The main function of the SR is to store calcium ions (Ca2+). Calcium in bio ...

in the cytoplasm, leading to massive

muscle contraction Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...

s. The effect of micromolar-level binding is

paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...

. This is true for both mammals and insects.

References

*
Essential Roles of Intracellular Calcium Release Channels in Muscle, Brain, Metabolism, and Aging
' Current Molecular Pharmacology vol.8, 2015, pages=206–222, * Bertil Hille, ''Ionic Channels of Excitable Membranes'', 2nd edition, Sinauer Associates, Sunderland, MA, 01375, Insecticides Pyrroles Carboxylate esters Alcohols Cyclopentanes Diterpene alkaloids Isopropyl compounds Plant toxins {{Alcohol-stub

See also

References