Question

Intracellular Ca2+ levels are important in cardiac muscle. Increasing intracellular Ca2+ levels in heart muscle cells leads to an increase in muscle contraction. Lowering the intracellular Ca2+ levels decreases the strength of cardiac muscle contraction.

Congestive heart failure can occur when the heart's pumping of blood is weaker than normal, which leads to fluid collecting around organs, including the heart. One treatment method is to give the patient drugs that increase the strength of the heart muscle contraction. Which of the following might function as an effective treatment of congestive heart failure by increasing the strength of heart muscle contraction? Choose one or more:
A. a drug that decreases the activity of the Na+/Ca2+ transporter
B. a drug that inhibits the Na+-K+ pump from establishing a strong Na+ gradient
C. a diuretic drug that triggers removal of excess Na+ from the body
D. a drug that blocks the calcium channel in heart muscle cells

Answer 1

For treating congestive heart failure, drugs that increase intracellular Ca2+ levels in cardiac muscle cells can be effective, such as those decreasing the Na+/Ca2+ transporter activity or inhibiting the Na+-K+ pump. Diuretics and calcium channel blockers would not directly increase the strength of heart muscle contractions.

Step-by-step explanation:

Intracellular Ca2+ levels are crucial for the contractile strength of cardiac muscle cells. To treat congestive heart failure by increasing the strength of heart muscle contraction, drugs that affect these levels can be effective. An ideal treatment would likely involve:

• A drug that decreases the activity of the Na+/sup>Ca2+ transporter would be effective because it would slow the removal of Ca2+ from inside the cell, increasing the intracellular concentration and thereby strengthening contractions.
• A drug that inhibits the Na+-K+ pump could potentially lead to an increased Na+ inside the cell, which indirectly contributes to reduced Ca2+ export through the Na+/sup>Ca2+ exchanger and hence an increase in intracellular Ca2+ level.
• A diuretic drug that triggers the removal of excess Na+ from the body can decrease the workload on the heart but does not directly increase the contractile strength of the heart muscle cells.

However, a drug that blocks the calcium channel in heart muscle cells would not be effective as treatment for congestive heart failure, as it would prevent the influx of Ca2+, leading to decreased intracellular Ca2+ levels and weaker contractions.