A soluble guanylate cyclase stimulator, BAY 41-8543, preserves right ventricular function in experimental pulmonary embolism.

Pulmonary embolism (PE) increases pulmonary vascular resistance, causing right ventricular (RV) dysfunction, and poor clinical outcome. Present studies test if the soluble guanylate cyclase stimulator BAY 41-8543 reduces pulmonary vascular resistance and protects RV function. Experimental PE was induced in anesthetized, male Sprague-Dawley rats by infusing 25 µm polystyrene microspheres (1.95 million/100 g body wt, right jugular vein) producing moderate PE. Pulmonary artery vascular resistance, estimated as RVPSP/CO, increased 3-fold after 5 h of PE. Treatment with BAY 41-8543 (50 µg/kg, I.V.; given at the time of PE induction) normalized this index by reducing RVPSP and markedly increasing CO, via preservation of heart rate and stroke volume. Ex vivo RV heart function showed minimal changes at 5 h of PE, but decreased significantly after 18 h of PE, including peak systolic pressure (PSP, Control 39 ± 1 mmHg vs. 19 ± 3 PE), +dP/dt (1192 ± 93 mmHg/s vs. 444 ± 64) and -dP/dt (-576 ± 60 mmHg/s vs. -278 ± 40). BAY 41-8543 significantly improved all three indices of RV heart function (PSP 35 ± 3.5, +dP/dt 1129 ± 100, -dP/dt -568 ± 87). Experimental PE produced increased PVR and RV dysfunction, which were ameliorated by treatment with BAY 41-8543. Thus, there is vasodilator reserve in this model of experimental PE that can be exploited to reduce the stress upon the heart and preserve RV contractile function.

Arginase depletes plasma l-arginine and decreases pulmonary vascular reserve during experimental pulmonary embolism.

The experiments test if experimental PE causes red blood cell hemolysis, arginase release and depletion of l-arginine and determine if arginase inhibition preserves l-arginine and improves pulmonary hemodynamics during PE. Experimental PE was induced in male Sprague-Dawley rats by infusing 25 µm microspheres (1.8 million/100 g body wt) in the jugular vein, producing moderate pulmonary hypertension. Pulmonary vascular resistance was estimated from the quotient of the right ventricular peak systolic pressure/cardiac output. Arterial plasma hemoglobin (ELISA), arginase activity (colorimetric assay) and l-arginine (high performance liquid chromatography) were determined. Arginase activity was inhibited by infusion of N-omega-hydroxy-nor-l-arginine (nor-NOHA, 400 mg/kg body wt, i.v.). Values are means ± s.e. Five hours of PE caused red blood cell hemolysis (15-fold increase in plasma hemoglobin) and release of arginase activity (2.7-fold increase). Plasma l-arginine concentration decreased significantly from 250 ± 20.6 to 118 ± 6.0 µmol/L (Control vs. PE) and estimated pulmonary vascular resistance increased 3-fold. Treatment with nor-NOHA prevented the depletion of plasma l-arginine (229 ± 15 µmol/L) and reduced the rise in pulmonary vascular resistance by 40%. In conclusion, experimental PE causes hemolysis, release of arginase activity, depletion of plasma l-arginine and increased estimated pulmonary vascular resistance. Inhibition of arginase activity preserves plasma l-arginine levels and improves estimated resistance, suggesting that the release of arginase during hemolysis contributes to the rise in estimated pulmonary resistance during experimental PE.

Proteomics of microparticles after experimental pulmonary embolism.

INTRODUCTION: Microparticles (MPs) are small fragments of apoptotic or activated cells that may contribute to pathological processes in cardiovascular diseases. In studies of MPs in clinical cohorts, it is unclear if observed changes in MP composition are a cause or a result of the cardiovascular disease being studied. The present studies employed a well-characterized rat model of experimental pulmonary embolism (PE) to determine if there were changes in MP characteristics as a result of pulmonary vascular occlusion. METHODS: PE was produced by infusing 25 µm polystyrene microspheres into the jugular vein of anesthetized rats. MPs were isolated by differential centrifugation of arterial blood 18 hr after PE. Proteins were separated by 1D gel electrophoresis and identified from tryptic digests by ultraperformance liquid chromatography (UPLC) coupled with tandem mass spectrometry. Statistical analysis was conducted using the Power Law Global Error Model (PLGEM). Changes in two proteins were confirmed by Western blot. RESULTS: Experimental PE produced pulmonary hypertension, mild systemic hypotension, hypoxia, hypercapnia and lactic acidosis. MPs showed significant elevation in proteins involved in clotting (fibronectin precursor, fibrinogen alpha, beta and gamma and von Willebrand factor) and several macroglobulin proteins, such as alpha-2-macroglobulin precursor compared with vehicle-treated control rats. Consistent with recent observations of hemolysis in PE, haptoglobin precursor protein, a major protein of hemoglobin clearance, decreased significantly in the PE animals. Plasma d-Dimer concentrations were significantly elevated, indicating that experimental PE produced a pro-coagulant state. CONCLUSIONS: These findings suggest that experimental PE produced significant, changes in MP characteristics to a prothrombotic phenotype.

Pulmonary vascular reserve during experimental pulmonary embolism: effects of a soluble guanylate cyclase stimulator, BAY 41-8543.

OBJECTIVES: Pulmonary embolism causes pulmonary hypertension by mechanical obstruction and vasoconstriction. Therapeutic potential of pharmacologic dilation of unblocked vessels has received limited attention. We tested pulmonary vasodilator reserve using a soluble guanylate cyclase stimulator, BAY 41-8543. DESIGN: Controlled animal study. SETTING: Medical center research laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Pulmonary embolism was induced by infusing 25-µm plastic microspheres in the right jugular vein, producing mild or moderate pulmonary hypertension. Control animals with no pulmonary embolism received suspension medium for microspheres. MEASUREMENTS AND MAIN RESULTS: Mild pulmonary embolism increased right ventricular peak systolic pressure (from 28 to 38 mm Hg) and decreased cardiac output (from 46 to 34 mL/min) with no change in mean arterial pressure. Infusion of BAY 41-8543 (50-200 µg/kg) decreased right ventricular peak systolic pressure. Five hrs moderate pulmonary embolism increased right ventricular peak systolic pressure (from 28 to 47 mm Hg) and decreased cardiac output (from 48 to 27 mL/min), causing right ventricular peak systolic pressure/cardiac output to increase from 0.6 control with no pulmonary embolism to 1.8 mm Hg/mL/min in 5-hr moderate pulmonary embolism + solvent for BAY 41-8543. Treatment of 5-hr moderate pulmonary embolism with BAY 41-8543 (50 µg/kg) caused a 2.2-fold increase in cardiac output (59 mL/min) with a 46% reduction in right ventricular peak systolic pressure (38 mm Hg), suggesting significant pulmonary vasodilation. Moderate pulmonary embolism decreased arterial sO2 (from 83% to 71%) and increased lactate (from 0.5 to 2.3 mmol/L). Treatment with BAY 41-8543 normalized sO2 and lactate. Hemolysis occurred during moderate experimental pulmonary embolism (60-fold increase in plasma hemoglobin). Treatment with BAY 41-8543 reduced free plasma hemoglobin content by 80%. CONCLUSIONS: In the setting of moderate impervious pulmonary embolism, treatment with a guanylate cyclase stimulator normalized pulmonary hemodynamics, reduced hemolysis, and improved oxygenation. These data support the hypothesis that pharmacologic dilation of nonobstructed pulmonary vasculature can effectively treat acute pulmonary hypertension from pulmonary embolism.