Which of the following is an effect of protamine sulfate?

Protamine sulfate is primarily used as an antidote to reverse the effects of heparin, an anticoagulant medication. When heparin is administered, it binds to antithrombin III, which in turn inhibits thrombin and factor Xa, leading to decreased coagulation or blood clot formation. Protamine sulfate works by binding to heparin and neutralizing its anticoagulant properties. This interaction effectively counteracts the effects of heparin, allowing for the restoration of normal blood clotting mechanisms.

Understanding the mechanism of action of protamine sulfate is crucial in situations where a patient has received too much heparin or when surgical or invasive procedures require rapid reversal of heparin’s effects. Neutralization of heparin activity is vital in managing bleeding complications and ensuring patient safety during treatment.

The other options either do not reflect the mechanism of protamine sulfate or pertain to other cardiovascular or smooth muscle dynamics unrelated to its primary action. Therefore, D is the correct answer as it accurately describes the therapeutic function of protamine sulfate in neutralizing heparin activity.