Streptokinase causes increase in –
**Core Concept**
Streptokinase is a thrombolytic agent used to dissolve blood clots and restore blood flow in conditions like acute ischemic stroke or myocardial infarction. It works by activating the fibrinolytic pathway, which leads to the breakdown of fibrin clots.
**Why the Correct Answer is Right**
The correct answer is **plasminogen**. Streptokinase binds to plasminogen, a circulating protein that is converted into its active form, plasmin. Plasmin then degrades fibrin clots, leading to their dissolution. This process is mediated by the fibrinolytic pathway, which involves the activation of plasminogen to plasmin by streptokinase.
**Why Each Wrong Option is Incorrect**
**Option A:** Fibrin - This is the opposite of what streptokinase does; it breaks down fibrin, the main component of blood clots.
**Option B:** Thrombin - Thrombin is an enzyme involved in clot formation, not clot dissolution. Streptokinase does not increase thrombin activity.
**Option C:** Prothrombin - Prothrombin is a precursor to thrombin and is not directly involved in the fibrinolytic pathway. Streptokinase does not affect prothrombin levels.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that thrombolytic therapy with streptokinase should be initiated within 3-4.5 hours of ischemic stroke onset to maximize benefits and minimize risks.
**Correct Answer:** D. Plasminogen