Cardiovascular agents affect the tone of pulmonary arteries and veins in precision-cut lung slices

Abstract

Introduction: Cardiovascular agents are pivotal in the therapy of heart failure. Apart from their action on ventricular contractility and systemic afterload, they affect pulmonary arteries and veins. Although these effects are crucial in heart failure with coexisting pulmonary hypertension or lung oedema, they are poorly defined, especially in pulmonary veins. Therefore, we investigated the pulmonary vascular effects of adrenoceptor agonists, vasopressin and angiotensin II in the model of precision-cut lung slices that allows simultaneous studies of pulmonary arteries and veins.

Materials and methods: Precision-cut lung slices were prepared from guinea pigs and imaged by videomicroscopy. Concentration-response curves of cardiovascular drugs were analysed in pulmonary arteries and veins.

Results: Pulmonary veins responded stronger than arteries to α(1)-agonists (contraction) and β(2)-agonists (relaxation). Notably, inhibition of β(2)-adrenoceptors unmasked the α(1)-mimetic effect of norepinephrine and epinephrine in pulmonary veins. Vasopressin and angiotensin II contracted pulmonary veins via V(1a) and AT(1) receptors, respectively, without affecting pulmonary arteries.

Discussion: Vasopressin and (nor)epinephrine in combination with β(2)-inhibition caused pulmonary venoconstriction. If applicable in humans, these treatments would enhance capillary hydrostatic pressures and lung oedema, suggesting their cautious use in left heart failure. Vice versa, the prevention of pulmonary venoconstriction by AT(1) receptor antagonists might contribute to their beneficial effects seen in left heart failure. Further, α(1)-mimetic agents might exacerbate pulmonary hypertension and right ventricular failure by contracting pulmonary arteries, whereas vasopressin might not.

Figure 1. Identification of pulmonary vessels.

A) A representative PCLS after staining with haematoxylin and eosin. B) epithelium of an airway (AW) C) Pulmonary artery (PA): endothelium with typical wrinkled inner lining and thick media D) Pulmonary vein (PV): endothelium without wrinkled inner lining and thin media E) corresponding unstained PCLS.

Figure 2. Responses of pulmonary arteries (PAs) to increasing dosages of adrenergic agents.

A-F) Pre-treatment concentrations were fixed. P<0.05 are considered as statistical significant and are indicated as followed p<0.05, p<0.01 and p<0.001.

Figure 3. Responses of pulmonary veins (PV) to adrenergic agents.

A) () isoproterenol (n = 5); (•) epinephrine (n = 6); (⧫) procaterol (n = 7); () norepinephrine (n = 6); B) (•) epinephrine (n = 6); (▪) prazosine (100 nM), epinephrine (n = 6); () ICI 118551 (100 nM), epinephrine (n = 5); (⋄) ICI 118551 (10 µM), epinephrine (n = 5); () procaterol, epinephrine (n = 4); C) (○) norepinephrine (n = 6); (□) prazosine (100 nM), norepinephrine (n = 3); () ICI 118551 (100 nM), norepinephrine (n = 9); (•) ICI 118551 (10 µM), norepinephrine (n = 6); () procaterol, norepinephrine (n = 4); D) (○) phenylephrine (n = 6); () A 61603 (n = 5), (□) ICI 118551 (100 nM), phenylephrine (n = 5). Asterics indicate different EC₅₀.values of the various curves. P<0.05 are considered as statistical significant and are indicated as followed p<0.05, p<0.01 and p<0.001.

Figure 4. Responses of pulmonary arteries (PAs) and pulmonary veins (PVs) to vasopressin.

A) PA: (•) vasopressin (n = 6); () indomethacin (10 µM), vasopressin (n = 4); (▪) L-NAME (100 µM), vasopressin (n = 5) B) PV: (•) vasopressin (n = 5); () indomethacin (10 µM), vasopressin (n = 4); (▪) L-NAME (100 µM), vasopressin (n = 5); () SR 49059 (10 nM), vasopressin (n = 3). C) PV: (•) vasopressin (n = 5); () vasopressin, SNAP (n = 7). D) PV: vasopressin, SNAP (n = 7). B) Asterics indicate different EC₅₀.values of the various curves. C–D) Statistics was performed using the Wilcoxon test. For all: P<0.05 are considered as statistical significant and are indicated as followed p<0.05, p<0.01 and p<0.001.

Figure 5. Responses of pulmonary arteries (PAs) and pulmonary veins (PVs) to L-NAME and SNAP.

A) (•) PV (n = 3); (○) PA (n = 3). B) (•) PV (n = 3); (○) PA (n = 3). Statistics was conducted using a linear mixed model analysis. P-values were adjusted for multiple comparisons by the false discovery rate. P<0.05 are considered as statistical significant and indicated as followed p<0.05, p<0.01 and p<0.001.

Figure 6. Responses of pulmonary arteries (PAs) and pulmonary veins (PVs) to angiotensin II.

A) PA: (•) angiotensin II (n = 6); () indomethacin (10 µM), angiotensin II (n = 5); (▪) L-NAME (100 µM), angiotensin II (n = 5) B) PV: (•) angiotensin II (n = 5); (▪) L-NAME (100 µM), angiotensin II (n = 5) C) PV: (•) angiotensin II (n = 5); () indomethacin (10 µM), angiotensin II (n = 5) D) PV: (•) angiotensin II (n = 5); () losartan (1 µM), angiotensin II (n = 3); (○) losartan (10 nM), angiotensin II (n = 3). Asterics indicate different EC₅₀.values of the various curves. P<0.05 are considered as statistical significant and are indicated as followed p<0.05, p<0.01 and p<0.001.