Cardiac glycosides are natural products that increase the intensity of heart muscle contraction. Among them are...

Cardiac glycosides are natural products that increase the intensity of heart muscle contraction. Among them are (a) digitalin – from digitalis, an extract of purple foxglove leaves and has been used to treat congestive heart failure for centuries and; (b) ouabain (pronounced wabane) – a product of the East African ouabio tree and has been long used as an arrow poison.
(a) What are the structures of these cardiac drugs?
(b) How do they affect the (Na+-K+)-ATPase? The cellular Na+ concentration? Explain the mechanisms.

Solutions

Expert Solution

The structure of the digitalis

The structure of the ouabain

In general Resting membrane potential is maintained by (Na+K+) ATPase, by pumping out three Na+ ions out of the cell for the exchange of two K+ ions.On Contrary action potential in muscle cells is initiated by the electrochemical gradiant across the muscle fibre membrane that is mediated by moving in more Na+ ions inside the cytoplasm by voltage gated Sodium channels. Action potential contracts the muscle where as resting potential helps muscles to be at rest.

Now Digitalis inhibits the action of (Na+K+) ATPase, that results in the accumulation of higher Na+ concentration inside the cells, Increase in Na+ ions concentration cause subsequence accumulation of Ca+ ions , that is via Ba+-Ca++ exchange system. Increase in intracellular concentration of Ca++ ions, results in release of more calcium by sarcoplasmic reticulum that bind to Troponin C which increases the contractility of the muscles.

gladiator answered 1 year ago

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