Reversal of reflex pulmonary vasoconstriction induced by main pulmonary arterial distension

1985 ◽  
Vol 58 (4) ◽  
pp. 1107-1114 ◽  
Author(s):  
C. E. Juratsch ◽  
R. F. Grover ◽  
C. E. Rose ◽  
J. T. Reeves ◽  
W. F. Walby ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Arachidonic Acid ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Bolus Injection ◽  
Main Pulmonary Artery ◽  
Pulmonary Vasoconstriction ◽  
Pulmonary Vasodilator ◽  
Anesthetized Dogs ◽  
The Right

Distension of the main pulmonary artery (MPA) induces pulmonary hypertension, most probably by neurogenic reflex pulmonary vasoconstriction, although constriction of the pulmonary vessels has not actually been demonstrated. In previous studies in dogs with increased pulmonary vascular resistance produced by airway hypoxia, exogenous arachidonic acid has led to the production of pulmonary vasodilator prostaglandins. Hence, in the present study, we investigated the effect of arachidonic acid in seven intact anesthetized dogs after pulmonary vascular resistance was increased by MPA distention. After steady-state pulmonary hypertension was established, arachidonic acid (1.0 mg/min) was infused into the right ventricle for 16 min; 15–20 min later a 16-mg bolus of arachidonic acid was injected. MPA distension was maintained throughout the study. Although the infusion of arachidonic acid significantly lowered the elevated pulmonary vascular resistance induced by MPA distension, the pulmonary vascular resistance returned to control levels only after the bolus injection of arachidonic acid. Notably, the bolus injection caused a biphasic response which first increased the pulmonary vascular resistance transiently before lowering it to control levels. In dogs with resting levels of pulmonary vascular resistance, administration of arachidonic acid in the same manner did not alter the pulmonary vascular resistance. It is concluded that MPA distension does indeed cause reflex pulmonary vasoconstriction which can be reversed by vasodilator metabolites of arachidonic acid. Even though this reflex may help maintain high pulmonary vascular resistance in the fetus, its function in the adult is obscure.

Endothelin-1 vasoactive responses in lambs with pulmonary hypertension and increased pulmonary blood flow

1995 ◽  
Vol 269 (6) ◽  
pp. H1965-H1972 ◽  
Author(s):  
J. Wong ◽  
V. M. Reddy ◽  
K. Hendricks-Munoz ◽  
J. R. Liddicoat ◽  
R. Gerrets ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Hypertension ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Pulmonary Blood Flow ◽  
Heart Diseases ◽  
Main Pulmonary Artery ◽  
Similar Degree ◽  
Fetal Sheep ◽  
Endothelin 1

Increased concentrations of endothelin-1 (ET-1) are found in children with congenital heart diseases that produce increased pulmonary blood flow and pulmonary hypertension, but the role of ET-1 in the pathophysiology of pulmonary hypertension is unclear. Therefore, we investigated ET-1-induced vasoactive responses and ET-1 concentrations in an animal model of pulmonary hypertension and increased pulmonary blood flow. Vascular shunts were placed between the ascending aorta and main pulmonary artery in seven late-gestation fetal sheep. Four weeks after spontaneous delivery, ET-1 increased pulmonary vascular resistance by 29.7 +/- 34.4% (P < 0.05), the ETb-receptor agonist [Ala1,3,11,15]ET-1 (4AlaET-1) had no effect, and the ETa-receptor antagonist cyclo(D-Asp-L-Pro-D-Val-L-Leu-D-Trp) (BQ-123) decreased pulmonary vascular resistance by -16.0 +/- 5.6% (P < 0.05). In contrast, in six control lambs with a similar degree of pulmonary hypertension induced by U-46619, ET-1 and 4AlaET-1 decreased pulmonary vascular resistance by 24.8 +/- 17.6, and 20.0 +/- 13.8%, respectively (P < 0.05). In addition, systemic arterial concentrations of immunoreactive ET-1 were elevated in lambs with pulmonary hypertension (29.2 +/- 9.6 vs. 15.2 +/- 10.7 pg/ml, P < 0.05). Pulmonary hypertension and increased pulmonary blood flow alters the response of ET-1 from pulmonary vasodilation to vasoconstriction. These altered responses suggest a role for ET-1 and its receptors in the pathogenesis of pulmonary hypertension secondary to increased pulmonary blood flow.

Analysis of pulmonary vasodilator responses to the Rho-kinase inhibitor fasudil in the anesthetized rat

2008 ◽  
Vol 295 (5) ◽  
pp. L828-L836 ◽  
Author(s):  
Adeleke M. Badejo ◽  
Jasdeep S. Dhaliwal ◽  
David B. Casey ◽  
Thomas B. Gallen ◽  
Anthony J. Greco ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Arterial Pressure ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Kinase Inhibitor ◽  
Rho Kinase ◽  
Systemic Arterial Pressure ◽  
Prior Exposure ◽  
Intravenous Injections ◽  
Pulmonary Vasodilator

The small GTP-binding protein Rho and its downstream effector, Rho-kinase, are important regulators of vasoconstrictor tone. Rho-kinase is upregulated in experimental models of pulmonary hypertension, and Rho-kinase inhibitors decrease pulmonary arterial pressure in rodents with monocrotaline and chronic hypoxia-induced pulmonary hypertension. However, less is known about responses to fasudil when pulmonary vascular resistance is elevated on an acute basis by vasoconstrictor agents and ventilatory hypoxia. In the present study, intravenous injections of fasudil reversed pulmonary hypertensive responses to intravenous infusion of the thromboxane receptor agonist, U-46619 and ventilation with a 10% O2 gas mixture and inhibited pulmonary vasoconstrictor responses to intravenous injections of angiotensin II, BAY K 8644, and U-46619 without prior exposure to agonists, which can upregulate Rho-kinase activity. The calcium channel blocker isradipine and fasudil had similar effects and in small doses had additive effects in blunting vasoconstrictor responses, suggesting parallel and series mechanisms in the lung. When pulmonary vascular resistance was increased with U-46619, fasudil produced similar decreases in pulmonary and systemic arterial pressure, whereas isradipine produced greater decreases in systemic arterial pressure. The hypoxic pressor response was enhanced by 5–10 mg/kg iv nitro-l-arginine methyl ester (l-NAME), and fasudil or isradipine reversed the pulmonary hypertensive response to hypoxia in control and in l-NAME-treated animals, suggesting that the response is mediated by Rho-kinase and L-type Ca2+ channels. These results suggest that Rho-kinase is constitutively active in regulating baseline tone and vasoconstrictor responses in the lung under physiological conditions and that Rho-kinase inhibition attenuates pulmonary vasoconstrictor responses to agents that act by different mechanisms without prior exposure to the agonist.

Pulmonary hemodynamics in respiratory acidosis in dogs

1963 ◽  
Vol 205 (5) ◽  
pp. 1008-1012 ◽  
Author(s):  
Leonard M. Linde ◽  
Daniel H. Simmons ◽  
Norman Lewis
Keyword(s):  
Cardiac Output ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Left Atrial ◽  
Respiratory Acidosis ◽  
Sham Operation ◽  
Pulmonary Hemodynamics ◽  
Acute Hemorrhage ◽  
Pulmonary Vasoconstriction ◽  
Anesthetized Dogs

Pulmonary vascular resistance of intact anesthetized dogs rose during constant ventilation with 5–8% CO2. This rise was not due to mechanical effects of decreased pulmonary artery or left atrial pressures or to decreased cardiac output, but appeared to be due to active pulmonary vasoconstriction. The increased pulmonary vascular resistance during CO2 breathing was eliminated by either adrenalectomy or sham operation, but not by acute hemorrhage, indicating that some mechanism other than blood loss accounted for the failure of response. This effect of operation may explain the variation in results previously reported. The mechanism is not known, but may be related to altering adrenal medullary secretions, which are known to cause pulmonary vasoconstriction. The response to CO2 was not restored in adrenalectomized animals by administration of maintenance or extra hydrocortisone, suggesting that the failure of pulmonary vascular resistance to rise in laparotomized animals was not due to adrenocortical depletion following surgery.

Thromboxane synthase inhibition and perinatal pulmonary response to arachidonic acid

1985 ◽  
Vol 58 (3) ◽  
pp. 710-716 ◽  
Author(s):  
M. L. Tod ◽  
S. Cassin
Keyword(s):  
Arachidonic Acid ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Pressor Response ◽  
Specific Inhibitor ◽  
Left Lobe ◽  
Pulmonary Response ◽  
Pulmonary Vasoconstriction ◽  
Lower Left Lobe

Arachidonic acid causes dose-dependent increases in pulmonary vascular resistance in perinatal lambs. The specific metabolites that produce this effect are not known; however, a role for thromboxanes (TX's), potent constrictors of vascular smooth muscle, has been proposed. The effects of a specific inhibitor of TX synthase, OKY-1581, were tested in newborn and ventilated fetal lambs using an in situ pump-perfused lower left lobe preparation. Pulmonary and systemic responses of newborns and ventilated fetuses to infusions of arachidonic acid were evaluated in the presence and absence of OKY-1581. Increases in pulmonary vascular resistance caused by arachidonic acid were diminished by TX synthase inhibition. The degree of systemic hypotension observed with arachidonic acid infusions was significantly greater in animals receiving OKY-1581 than in animals without the inhibitor. The effect of OKY-1581 on periods of hypoxia was also evaluated in newborn lambs. There were no significant differences in the hypoxic pressor response in lambs with and without TX synthase inhibition. These results suggest that OKY-1581 can reduce most of the pulmonary vasoconstriction produced by arachidonic acid in perinatal lambs.

Pulmonary Vascular Versus Right Ventricular Function Changes During Targeted Therapies of Pulmonary Hypertension – An Argument for Upfront Combination Therapy?

2012 ◽  
Vol 8 (3) ◽  
pp. 209
Author(s):  
Wouter Jacobs ◽  
Anton Vonk-Noordegraaf ◽  
◽  
Keyword(s):  
Combination Therapy ◽  
Right Ventricle ◽  
Right Ventricular ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Meta Analysis ◽  
Right Heart Failure ◽  
Functional Class ◽  
Pulmonary Vasculature ◽  
The Right

Pulmonary arterial hypertension is a progressive disease of the pulmonary vasculature, ultimately leading to right heart failure and death. Current treatment is aimed at targeting three different pathways: the prostacyclin, endothelin and nitric oxide pathways. These therapies improve functional class, increase exercise capacity and improve haemodynamics. In addition, data from a meta-analysis provide compelling evidence of improved survival. Despite these treatments, the outcome is still grim and the cause of death is inevitable – right ventricular failure. One explanation for this paradox of haemodynamic benefit and still worse outcome is that the right ventricle does not benefit from a modest reduction in pulmonary vascular resistance. This article describes the physiological concepts that might underlie this paradox. Based on these concepts, we argue that not only a significant reduction in pulmonary vascular resistance, but also a significant reduction in pulmonary artery pressure is required to save the right ventricle. Haemodynamic data from clinical trials hold the promise that these haemodynamic requirements might be met if upfront combination therapy is used.

scholarly journals Sex Dimorphism in Pulmonary Hypertension: The Role of the Sex Chromosomes

Antioxidants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 779
Author(s):  
Daria S. Kostyunina ◽  
Paul McLoughlin
Keyword(s):  
Pulmonary Hypertension ◽  
Pulmonary Arterial Hypertension ◽  
Arterial Hypertension ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Sex Chromosomes ◽  
Bone Morphogenetic Protein 2 ◽  
Sex Dimorphism ◽  
Pulmonary Arterial ◽  
The Impact

Pulmonary hypertension (PH) is a condition characterised by an abnormal elevation of pulmonary artery pressure caused by an increased pulmonary vascular resistance, frequently leading to right ventricular failure and reduced survival. Marked sexual dimorphism is observed in patients with pulmonary arterial hypertension, a form of pulmonary hypertension with a particularly severe clinical course. The incidence in females is 2–4 times greater than in males, although the disease is less severe in females. We review the contribution of the sex chromosomes to this sex dimorphism highlighting the impact of proteins, microRNAs and long non-coding RNAs encoded on the X and Y chromosomes. These genes are centrally involved in the cellular pathways that cause increased pulmonary vascular resistance including the production of reactive oxygen species, altered metabolism, apoptosis, inflammation, vasoconstriction and vascular remodelling. The interaction with genetic mutations on autosomal genes that cause heritable pulmonary arterial hypertension such as bone morphogenetic protein 2 (BMPR2) are examined. The mechanisms that can lead to differences in the expression of genes located on the X chromosomes between females and males are also reviewed. A better understanding of the mechanisms of sex dimorphism in this disease will contribute to the development of more effective therapies for both women and men.

scholarly journals Inhaled Nitric Oxide at Birth Reduces Pulmonary Vascular Resistance and Improves Oxygenation in Preterm Lambs

Children ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 378
Author(s):  
Satyan Lakshminrusimha ◽  
Sylvia F. Gugino ◽  
Krishnamurthy Sekar ◽  
Stephen Wedgwood ◽  
Carmon Koenigsknecht ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Pulmonary Hypertension ◽  
Pulmonary Vascular Resistance ◽  
Preterm Infants ◽  
Vascular Resistance ◽  
Inhaled Nitric Oxide ◽  
Persistent Pulmonary Hypertension ◽  
Inhaled No ◽  
Birth Preterm

Resuscitation with 21% O2 may not achieve target oxygenation in preterm infants and in neonates with persistent pulmonary hypertension of the newborn (PPHN). Inhaled nitric oxide (iNO) at birth can reduce pulmonary vascular resistance (PVR) and improve PaO2. We studied the effect of iNO on oxygenation and changes in PVR in preterm lambs with and without PPHN during resuscitation and stabilization at birth. Preterm lambs with and without PPHN (induced by antenatal ductal ligation) were delivered at 134 d gestation (term is 147–150 d). Lambs without PPHN were ventilated with 21% O2, titrated O2 to maintain target oxygenation or 21% O2 + iNO (20 ppm) at birth for 30 min. Preterm lambs with PPHN were ventilated with 50% O2, titrated O2 or 50% O2 + iNO. Resuscitation with 21% O2 in preterm lambs and 50%O2 in PPHN lambs did not achieve target oxygenation. Inhaled NO significantly decreased PVR in all lambs and increased PaO2 in preterm lambs ventilated with 21% O2 similar to that achieved by titrated O2 (41 ± 9% at 30 min). Inhaled NO increased PaO2 to 45 ± 13, 45 ± 20 and 76 ± 11 mmHg with 50% O2, titrated O2 up to 100% and 50% O2 + iNO, respectively, in PPHN lambs. We concluded that iNO at birth reduces PVR and FiO2 required to achieve target PaO2.

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