Chronic hypoxic pulmonary hypertension. Is thrombin involved?

Area of Science:

• Cardiovascular Research
• Pulmonary Medicine
• Pharmacology

Background:

• Thrombin plays a role in vascular smooth muscle contraction and proliferation.
• Pulmonary hypertension involves vasoconstriction and vascular remodeling.
• The specific contribution of thrombin to hypoxic pulmonary hypertension is not fully understood.

Purpose of the Study:

• To investigate the role of thrombin in the development of chronic hypoxic pulmonary hypertension.
• To determine if inhibiting thrombin with hirudin can prevent or mitigate pulmonary hypertension induced by hypobaric hypoxia.

Main Methods:

• Rats were exposed to hypobaric hypoxia (HH) for 3 weeks.
• Hirudin, a specific thrombin inhibitor, was administered intravenously to one group of hypoxic rats.
• Control groups received either saline (hypoxic control, HC) or were maintained in normoxic conditions (normoxic control, NC).
• Thrombin activity was confirmed by plasma clotting assays.
• Hemodynamic parameters, right ventricle weight, and lung vascular morphology were assessed.

Main Results:

• Hirudin administration confirmed sufficient thrombin inhibition in HH rats.
• A slight reduction in mean pulmonary arterial pressure was observed with hirudin, but it was not statistically significant.
• No significant differences were found between hirudin-treated and control hypoxic groups in pulmonary resistance, right ventricle hypertrophy, or lung vascular remodeling.
• Hirudin did not affect vasoconstrictor responses to angiotensin II or acute hypoxia.

Conclusions:

• Thrombin inhibition with hirudin does not significantly prevent the development of chronic hypoxic pulmonary hypertension in rats.
• The study suggests that thrombin's catalytic effect on fibrinogen may not be a primary driver of this specific model of pulmonary hypertension.