Cardiac glycoside 7296 223054797 2008-07-02T10:56:29Z BOTarate 5870361 robot Adding: [[es:Glucósido cardiaco]] '''Cardiac glycosides''' are [[medication|drugs]] used in the treatment of [[congestive heart failure]] and cardiac [[arrhythmia]]. These [[glycoside]]s are found as [[secondary metabolite]]s in several [[plant]]s, but also in some animals. Some of these compounds ([[ouabain]] and some frog poisons) are used in Africa as arrow-poisons for hunting. ==Function== Cardiac glycosides work by inhibiting the [[NaKATPase|Na<sup>+</sup>/K<sup>+</sup> pump]]. This causes an increase in the level of [[sodium]] [[ion]]s in the myocytes, which then leads to a rise in the level of [[calcium]] ions. This inhibition increases the amount of [[Calcium|Ca]]<sup>2+</sup> [[ion]]s available for contraction of the heart [[muscle]], improves cardiac output and reduces distention of the heart. They do this by stabilizing the E2-P transition state of the [[NaKATPase|Na<sup>+</sup>/K<sup>+</sup> pump]]. The proposed mechanism is the following: inhibition of the Na<sup>+</sup>/K<sup>+</sup> pump leads to increased Na<sup>+</sup> levels, which in turn slows down the extrusion of Ca<sup>2+</sup> via the [[Sodium-calcium exchanger|Na<sup>+</sup>/Ca<sup>2+</sup> exchange pump]]. Increased amounts of Ca<sup>2+</sup> are then stored in the [[sarcoplasmic reticulum]] and released by each [[action potential]]. They have an [[antiarrhythmic]] effect by prolonging the refractory period of the AV node ([[Atrioventricular node]]), reducing the number of impulses reaching the [[Ventricle (heart)|ventricle]]s. Cardiac output is restored but [[atrial fibrillation]] or atrial flutter are not abolished. ==Examples== Examples of plants producing cardiac glycosides: * ''[[Strophanthus]]'' - [[ouabain]] g/k/e-strophanthin * ''[[Digitalis]] lanata'' and ''Digitalis purpurea'' - [[digoxin]], [[digitoxin]] * ''[[Urginea maritima|Scilla maritima]]'' - proscillaridine A * ''Adonis vernalis, Adonis aestivalis'' * ''Acokanthera oblongifolia'' * ''[[Convallaria]]'' (lily of the valley) Some frog-poison contain [[bufalin]], [[marinobufagenin]] and [[bufadienolide]]s, cardiac glycosides. ==See also== *[[Cardenolide aglycones]] ==External links== {{Glycosides}} {{Cardiac glycosides}} [[Category:Cardiac glycosides| ]] [[Category:Glycosides]] [[cs:Srdeční glykosidy]] [[de:Herzglykoside]] [[et:Südameglükosiidid]] [[es:Glucósido cardiaco]] [[fr:Glycoside cardiotonique]] [[ja:強心配糖体]] [[pl:Glikozydy nasercowe]] [[pt:Cardioglicosideo]] [[vi:Glicozit tim]] [[zh:强心甙类]]