Suppose a lackadaisical Ethiopian cook drops a leaf from the

Suppose a lackadaisical Ethiopian cook drops a leaf from the East African Ouabio tree into your soup. After you drink the soup, your heart starts beating with greater force. Give a molecular explanation of what happened.

Hint1: A rise in the intracellular Ca2+ conc causes cardiac muscle cells to contract.

Hint2: An antiporter exchanges Ca2+ for extracellular Na+ across the plasma membrane

           and causes cardiac muscle cells to relax .

Hint3: Ouabain inhibits Na+-K+ pump.

Solution

Ouabain -  (a product of the East African Ouabio tree) - cardiac glycoside. It\'s a potent and specific inhibitor of the Na⁺-K⁺ ATPase - has long been used as an arrow poison.

Inhibiting the Na⁺-K⁺-ATPase makes the heart contract more strongly. Inhibits the Na⁺-K⁺ ATPase transport system, leading to a loss of K⁺ from the heart cells and an increase of Na⁺ in heart cells. The increased Na⁺ activates a Na⁺-Ca²⁺ pump that exchanges intracellular Na⁺ for extracellular Ca²⁺. The increase in intracellular Ca²⁺ enhances myocardial contraction.