Lusitropia
As lusitropy influencing the ability of the heart muscle (is myocardium ) means for rapid and complete relaxation. It forms the functional opposite of inotropy (contractility), but is just as important for the mechanical pumping action of the heart. Positive lusitropia means an increase in the ability to relax, and negative lusitropia means the corresponding decrease. Lusitropia depends largely on the speed of calcium transport from the cytoplasm .
Positive lusitropia
The binding of catecholamines ( noradrenaline from local sympathetic varicosities as well as noradrenaline and adrenaline from the adrenal medulla ) to β 1 -adrenoceptors sets the signal chain
- G-protein coupled receptor → activated G α → adenylyl cyclase → cAMP → protein kinase A.
in progress. PKA phosphorylates phospholamban , which otherwise inhibits sarcoplasmic Ca 2+ -ATPase ( SERCA ). As a result of the disinhibition, more Ca 2+ is pumped from the cytoplasm back into the sarcoplasmic reticulum over time , so that the heart muscle cell can relax more quickly.
The PKA also phosphorylates troponin I, which lowers the affinity of troponin C for calcium, so that the activation of the myofibrils is terminated more quickly.
Negative lusitropia
Cardiac glycosides have a negative lusitropic effect by inhibiting the transport of calcium from the cytoplasm . The desired effect of these drugs is increased inotropy.
Individual evidence
- ↑ JC Behrends et al .: Physiology (Dual Series) . 1st edition. Thieme, Stuttgart 2010, ISBN 978-3-13-138411-9 , p. 102 .
- ^ Robert Franz Schmidt , Florian Lang, Manfred Heckmann (eds.): Physiology of humans . 31st edition. Springer Medizin Verlag, Heidelberg 2010, ISBN 978-3-642-01650-9 , p. 521 .