18. (10 points) Ouabain is a cardiac glycoside that has been used to treat atria
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18. (10 points) Ouabain is a cardiac glycoside that has been used to treat atrial fibrillation and congestive heart failure in humans. It is a specific inhibitor of the Na*K -pump. You do a series of experiments to determine the mechanism by which the inhibitor works. What do each of the following results tell you about ouabain's inhibition of the pump? A) Ouabain added to a solution containing intact cells inhibits movement of ions across the plasma membrane (K in and Na out). Ouabain injected into individual cells does not inhibit the movement of the ions across the cell membrane. B) Ouabain is added to a solution containing intact cells and allowed to affect full inhibition of the pump. The cells are then collected so that the membrane proteins can be studied. All the Na+K+-pumps from the ouabain-treated cells are found to be in the phosphorylated formExplanation / Answer
Ouabain a toxic compound obtained from certain trees, used as a very rapid cardiac stimulant. It is a polycyclic glycoside that was traditionally used as an arrow poison in eastern Africa for both hunting and warfare.
The Na/K pump establishes essential ion concentration gradients across animal cell membranes. Na, K-ATPase is extremely essential for solute and water transport in cells, and ouabain generally blocks fluid secretion in these cells. By binding to the Na, K-ATPase, ouabain induces proliferation in some cell types.
18 (A) Here ouabain injected into cells doesn't inhibit movement of ions across the membrane. It has been reported that a Low Dose Ouabain Stimulates Na-K ATPase ?1 subunit Association with Angiotensin II Type 1 Receptor in Renal Proximal Tubule Cells. Thus the individual cell might be the Renal Proximal Tubule Cells and hence this phenomenon.
18 (B) The ATP binding and phosphorylation-dephosphorylation reactions generally drives conformational changes that alternately open and close each gate to exchange ions at the cell interior or exterior while ensuring that both are never open at a time. It has been reported that Ouabain-sensitive ATPase activity and the phosphorylation of Na, K-ATPase in the absence of sodium ions. Hence this report holds true.
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