Which of the following effects of the steroid digitalis is observed after treatment of congestive heart failure a. decrease in cytosolic sodium levels. b. inhib

Abhijeet Gaurav Best Answer

Answer is option (B). Digitalis compounds are potent inhibitors of cellular Na+/K+-ATPase. This ion transport system moves sodium ions out of the cell and brings potassium ions into the cell. This transport function is necessary for cell survival because sodium diffusion into the cell and potassium diffusion out of the cell down their concentration gradients would reduce their concentration differences (gradients) across the cell membrane over time. Loss of these ion gradients would lead to cellular depolarization and loss of the negative membrane potential that is required for normal cell function. The Na+/K+-ATPase also plays an active role in the membrane potential. this pump is electrogenic because it transports 3 sodium ions out of the cell for every 2 potassium ions that enter the cell. This can add several negative millivolts to the membrane potential depending on the activity of the pump.By inhibiting the Na+/K+-ATPase, cardiac glycosides cause intracellular sodium concentration to increase. This then leads to an accumulation of intracellular calcium via the Na+-Ca++ exchange system. In the heart, increased intracellular calcium causes more calcium to be released by the sarcoplasmic reticulum, thereby making more calcium available to bind to troponin-C, which increases contractility (inotropy). Inhibition of the Na+/K+-ATPase in vascular smooth muscle causes depolarization, which causes smooth muscle contraction and vasoconstriction.