MECHANISM


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After 200 years after its discovery by Withering, the exact mode of action of glycosides remains unknown. Most researcher agree on the following basic mechanism:

Increased glycoside concentrations near the heart cell, cause an inhibiting effect on the cell membranes potassium-sodium-ATPase.

As a result, there is a slowinge extracellualr space. The increased Na ions in the cell cause the Calcium ions to be displaced from the calcium receptor sites on the sarcoplastic reticulum. This increased cell calcium binds with tropomyosin. This causes the decrease in actin-myosin inhibition, which leads to myocardial cell contraction.







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