Acute and chronic hypoxic pulmonary hypertension in guinea pigs

1989 ◽  
Vol 66 (2) ◽  
pp. 920-928 ◽  
Author(s):  
B. T. Thompson ◽  
P. M. Hassoun ◽  
R. L. Kradin ◽  
C. A. Hales
Keyword(s):  
Pulmonary Hypertension ◽  
Cardiac Index ◽  
Guinea Pigs ◽  
Chronic Hypoxia ◽  
Acute Hypoxia ◽  
Pulmonary Arteries ◽  
Initial Response ◽  
Hypoxic Pulmonary Hypertension ◽  
Mean Pulmonary Arterial Pressure ◽  
Chronic Pulmonary Hypertension

To determine whether the strength of acute hypoxic vasoconstriction predicts the magnitude of chronic hypoxic pulmonary hypertension, we performed serial studies on guinea pigs. Unanesthetized, chronically catheterized guinea pigs increased mean pulmonary arterial pressure (PAP) from 11 +/- 0.5 to 13 +/- 0.7 Torr in acute hypoxia (10% O2 for 65 min). The response was maximal at 5 min, remained stable for 1 h, and was reversible on return to room air. Cardiac index did not change with acute hypoxia or recovery. Guinea pigs exposed to chronic hypoxia increased PAP, measured in room air 1 h after removal from the hypoxic chamber, to 18 +/- 1 Torr by 5 days with little further increase in PAP to 20 +/- 1 Torr after 21 days. Cardiac index fell from 273 +/- 12 to 206 +/- 7 ml.kg-1.min-1 (P less than 0.05) after 21 days of hypoxia. Medial thickness of pulmonary arteries adjacent to terminal bronchioles and alveolar ducts increased significantly by 10 days. The magnitude of the pulmonary vasoconstriction to acute hypoxia persisted and was unabated during the development and apparent stabilization of chronic hypoxic pulmonary hypertension, suggesting that if vasoconstriction is the stimulus for remodeling, then the importance of the stimulus lessens with duration of hypoxia. In individual animals followed serially, we found no correlation between the magnitude of the acute vasoconstrictor response before chronic hypoxia and the severity of chronic pulmonary hypertension that subsequently developed either because the initial response was small and variable or because vasoconstriction may not be the sole stimulus for vascular remodeling in the guinea pig.

Chronic EDRF inhibition and hypoxia: effects on pulmonary circulation and systemic blood pressure

1993 ◽  
Vol 75 (4) ◽  
pp. 1748-1757 ◽  
Author(s):  
V. Hampl ◽  
S. L. Archer ◽  
D. P. Nelson ◽  
E. K. Weir
Keyword(s):  
Pulmonary Hypertension ◽  
Arterial Pressure ◽  
Chronic Hypoxia ◽  
Acute Hypoxia ◽  
Systemic Blood Pressure ◽  
Systemic Circulation ◽  
Systemic Arterial Pressure ◽  
Hypoxic Pulmonary Hypertension ◽  
Basal Tone ◽  
Isolated Lungs

It has been suggested that chronic hypoxic pulmonary hypertension results from chronic hypoxic inhibition of endothelium-derived relaxing factor (EDRF) synthesis. We tested this hypothesis by studying whether chronic EDRF inhibition by N omega-nitro-L-arginine methyl ester (L-NAME) would induce pulmonary hypertension similar to that found in chronic hypoxia. L-NAME (1.85 mM) was given for 3 wk in drinking water to rats living in normoxia or hypoxia. Unlike chronic hypoxia, chronic L-NAME treatment did not increase pulmonary arterial pressure. Cardiac output was reduced and mean systemic arterial pressure was increased by chronic L-NAME treatment. The vascular pressure-flow relationship in isolated lungs was shifted toward higher pressures by chronic hypoxia and, to a lesser degree, by L-NAME intake. In isolated lungs, vasoconstriction in response to angiotensin II and acute hypoxia and vasodilation in response to sodium nitroprusside were increased by chronic L-NAME treatment in normoxia and chronic hypoxia. Chronic hypoxia, but not L-NAME, induced hypertensive pulmonary vascular remodeling. Chronic supplementation with the EDRF precursor L-arginine did not have any significant effect on chronic hypoxic pulmonary hypertension. We conclude that the chronic EDRF deficiency state, induced by L-NAME, does not mimic chronic hypoxic pulmonary hypertension in our model. In addition, EDRF proved to be less important for basal tone regulation in the pulmonary than in the systemic circulation.

Polycythemia and vascular remodeling in chronic hypoxic pulmonary hypertension in guinea pigs

1991 ◽  
Vol 71 (6) ◽  
pp. 2218-2223 ◽  
Author(s):  
S. P. Janssens ◽  
B. T. Thompson ◽  
C. R. Spence ◽  
C. A. Hales
Keyword(s):  
Pulmonary Hypertension ◽  
Guinea Pigs ◽  
Vascular Remodeling ◽  
Chronic Hypoxia ◽  
Pulmonary Arterial Pressure ◽  
Pulmonary Arteries ◽  
Similar Degree ◽  
Similar Tendency ◽  
Pulmonary Arterial ◽  
Medial Thickening

Chronic hypoxia increases pulmonary arterial pressure (PAP) as a result of vasoconstriction, polycythemia, and vascular remodeling with medial thickening. To determine whether preventing the polycythemia with repeated bleeding would diminish the pulmonary hypertension and remodeling, we compared hemodynamic and histological profiles in hypoxic bled (HB, n = 6) and hypoxic polycythemic guinea pigs (H, n = 6). After 10 days in hypoxia (10% O2), PAP was increased from 10 +/- 1 (SE) mmHg in room air controls (RA, n = 5) to 20 +/- 1 mmHg in H (P less than 0.05) but was lower in HB (15 +/- 1 mmHg, P less than 0.05 vs. H). Cardiac output and pulmonary artery vasoreactivity did not differ among groups. Total pulmonary vascular resistance increased from 0.072 +/- 0.011 mmHg.ml-1.min in RA to 0.131 mmHg.ml-1.min in H but was significantly lower in HB (0.109 +/- 0.006 mmHg.ml-1.min). Hematocrit increased with hypoxia (57 +/- 3% in H vs. 42 +/- 1% in RA, P less than 0.05), and bleeding prevented the increase (46 +/- 4% in HB, P less than 0.05 vs. H only). The proportion of thick-walled peripheral pulmonary vessels (53.2 +/- 2.9% in HB and 50.6 +/- 4.8% in H vs. 31.6 +/- 2.6% in RA, P less than 0.05) and the percent medial thickness of pulmonary arteries adjacent to alveolar ducts (7.2 +/- 0.6% in HB and 7.0 +/- 0.4% in H vs. 5.2 +/- 0.4% in RA, P less than 0.05) increased to a similar degree in both hypoxic groups. A similar tendency was present in larger bronchiolar vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Role of ASIC1 in the development of chronic hypoxia-induced pulmonary hypertension

2014 ◽  
Vol 306 (1) ◽  
pp. H41-H52 ◽  
Author(s):  
Carlos H. Nitta ◽  
David A. Osmond ◽  
Lindsay M. Herbert ◽  
Britta F. Beasley ◽  
Thomas C. Resta ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Chronic Hypoxia ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Acute Hypoxia ◽  
Pulmonary Arteries ◽  
Systolic Pressure ◽  
Arterial Remodeling ◽  
Ventricular Systolic Pressure ◽  
Intracellular Ca

Chronic hypoxia (CH) associated with respiratory disease results in elevated pulmonary vascular intracellular Ca2+ concentration, which elicits enhanced vasoconstriction and promotes vascular arterial remodeling and thus has important implications in the development of pulmonary hypertension (PH). Store-operated Ca2+ entry (SOCE) contributes to this elevated intracellular Ca2+ concentration and has also been linked to acute hypoxic pulmonary vasoconstriction (HPV). Since our laboratory has recently demonstrated an important role for acid-sensing ion channel 1 (ASIC1) in mediating SOCE, we hypothesized that ASIC1 contributes to both HPV and the development of CH-induced PH. To test this hypothesis, we examined responses to acute hypoxia in isolated lungs and assessed the effects of CH on indexes of PH, arterial remodeling, and vasoconstrictor reactivity in wild-type (ASIC1+/+) and ASIC1 knockout (ASIC1−/−) mice. Restoration of ASIC1 expression in pulmonary arterial smooth muscle cells from ASIC1−/− mice rescued SOCE, confirming the requirement for ASIC1 in this response. HPV responses were blunted in lungs from ASIC1−/− mice. Both SOCE and receptor-mediated Ca2+ entry, along with agonist-dependent vasoconstrictor responses, were diminished in small pulmonary arteries from control ASIC−/− mice compared with ASIC+/+ mice. The effects of CH to augment receptor-mediated vasoconstrictor and SOCE responses in vessels from ASIC1+/+ mice were not observed after CH in ASIC1−/− mice. In addition, ASIC1−/− mice exhibited diminished right ventricular systolic pressure, right ventricular hypertrophy, and arterial remodeling in response to CH compared with ASIC1+/+ mice. Taken together, these data demonstrate an important role for ASIC1 in both HPV and the development of CH-induced PH.

scholarly journals Exposure of mice to chronic hypoxia attenuates pulmonary arterial contractile responses to acute hypoxia by increases in extracellular hydrogen peroxide

2014 ◽  
Vol 307 (4) ◽  
pp. R426-R433 ◽  
Author(s):  
Dhara Patel ◽  
Raed Alhawaj ◽  
Michael S. Wolin
Keyword(s):  
Hydrogen Peroxide ◽  
Pulmonary Hypertension ◽  
Chronic Hypoxia ◽  
Soluble Guanylate Cyclase ◽  
Aminolevulinic Acid ◽  
Acute Hypoxia ◽  
Pulmonary Arteries ◽  
Protoporphyrin Ix

Exposing mice to a chronic hypoxic treatment (10% oxygen, 21 days) that promotes pulmonary hypertension was observed to attenuate the pulmonary vasoconstriction response to acute hypoxia (HPV) both in vivo and in isolated pulmonary arteries. Since catalase restored the HPV response in isolated arteries, it appeared to be attenuated by extracellular hydrogen peroxide. Chronic hypoxia promoted the detection of elevated lung superoxide, extracellular peroxide, extracellular SOD expression, and protein kinase G (PKG) activation [based on PKG dimerization and vasodilator-stimulated phosphoprotein (VASP) phosphorylation], suggesting increased generation of extracellular peroxide and PKG activation may contribute to the suppression of HPV. Aorta from mice exposed to 21 days of hypoxia also showed evidence for extracellular hydrogen peroxide, suppressing the relaxation response to acute hypoxia. Peroxide appeared to partially suppress contractions to phenylephrine used in the study of in vitro hypoxic responses. Treatment of mice with the heme precursor δ-aminolevulinic acid (ALA; 50 mg·kg−1·day−1) during exposure to chronic hypoxia was examined as a pulmonary hypertension therapy because it could potentially activate beneficial cGMP-mediated effects through promoting a prolonged protoporphyrin IX (PpIX)-elicited activation of soluble guanylate cyclase. ALA attenuated pulmonary hypertension, increases in both superoxide and peroxide, and the suppression of in vitro and in vivo HPV responses. ALA generated prolonged detectible increases in PpIX and PKG-associated phosphorylation of VASP, suggesting PKG activation may contribute to suppression of pulmonary hypertension and prevention of alterations in extracellular peroxide that appear to be attenuating HPV responses caused by chronic hypoxia.

Effect of dietary fish oil on lung lipid profile and hypoxic pulmonary hypertension

1989 ◽  
Vol 66 (4) ◽  
pp. 1662-1673 ◽  
Author(s):  
S. L. Archer ◽  
G. J. Johnson ◽  
R. L. Gebhard ◽  
W. L. Castleman ◽  
A. S. Levine ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Fish Oil ◽  
Chronic Hypoxia ◽  
Corn Oil ◽  
Pulmonary Arteries ◽  
Hypoxic Pulmonary Hypertension ◽  
Dietary Fish ◽  
Lung Lipid ◽  
Pulmonary Arterial ◽  
Fish Oil Diet

The effects of dietary polyunsaturated fats on chronic hypoxic pulmonary hypertension were assessed in rats fed fish oil, corn oil, or a lower fat, “high-carbohydrate” diet (regular) beginning 1 mo before the start of hypoxia (0.4 atm, n = 30 for each). Mean pulmonary arterial pressures were lower in the chronically hypoxic rats fed fish oil (19.7 +/- 1.8 mm Hg) than in the rats fed corn oil (25.3 +/- 1.6 mm Hg) or regular diets (27.5 +/- 1.5 mm Hg, P less than 0.05). The fish oil diet increased lung eicosapentaenoic acid 50-fold and depleted lung arachidonic acid 60% (P less than 0.0001 for each). Lung thromboxane B2 and 6-ketoprostaglandin F1 alpha levels were lower, and platelet aggregation, in response to collagen, was reduced in rats fed fish oil. Chronically hypoxic rats fed fish oil had lower mortality rates than the other hypoxic rats. They also had lower blood viscosity, as well as less right ventricular hypertrophy and less peripheral extension of vascular smooth muscle to intra-acinar pulmonary arteries (P less than 0.05 for each). The mechanism by which dietary fish oil decreases pulmonary hypertension and vascular remodeling during chronic hypoxia remains uncertain. The finding that a fish oil diet can reduce the hemodynamic and morphological sequelae of chronic hypoxia may have therapeutic significance.

Store-operated channels in the pulmonary circulation of high- and low-altitude neonatal lambs

2013 ◽  
Vol 304 (8) ◽  
pp. L540-L548 ◽  
Author(s):  
Daniela Parrau ◽  
Germán Ebensperger ◽  
Emilio A. Herrera ◽  
Fernando Moraga ◽  
Raquel A. Riquelme ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Vascular Resistance ◽  
Vascular Reactivity ◽  
Chronic Hypoxia ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Acute Hypoxia ◽  
Pulmonary Arteries ◽  
Arterial Blood ◽  
Low Altitude

We determined whether store-operated channels (SOC) are involved in neonatal pulmonary artery function under conditions of acute and chronic hypoxia, using newborn sheep gestated and born either at high altitude (HA, 3,600 m) or low altitude (LA, 520 m). Cardiopulmonary variables were recorded in vivo, with and without SOC blockade by 2-aminoethyldiphenylborinate (2-APB), during basal or acute hypoxic conditions. 2-APB did not have effects on basal mean pulmonary arterial pressure (mPAP), cardiac output, systemic arterial blood pressure, or systemic vascular resistance in both groups of neonates. During acute hypoxia 2-APB reduced mPAP and pulmonary vascular resistance in LA and HA, but this reduction was greater in HA. In addition, isolated pulmonary arteries mounted in a wire myograph were assessed for vascular reactivity. HA arteries showed a greater relaxation and sensitivity to SOC blockers than LA arteries. The pulmonary expression of two SOC-forming subunits, TRPC4 and STIM1, was upregulated in HA. Taken together, our results show that SOC contribute to hypoxic pulmonary vasoconstriction in newborn sheep and that SOC are upregulated by chronic hypoxia. Therefore, SOC may contribute to the development of neonatal pulmonary hypertension. We propose SOC channels could be potential targets to treat neonatal pulmonary hypertension.

Comparative physiology of hypoxic pulmonary hypertension: historical clues from brisket disease

2005 ◽  
Vol 98 (3) ◽  
pp. 1092-1100 ◽  
Author(s):  
Jann Rhodes
Keyword(s):  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Chronic Hypoxia ◽  
Splice Variants ◽  
Pulmonary Arteries ◽  
High Mountain ◽  
Hypoxic Pulmonary Hypertension ◽  
And Gender ◽  
Medial Hypertrophy

Some of the most valuable contributions to science have come about serendipitously, and, in 1913, when George Glover and Issac Newsom were commissioned by Colorado cattle ranchers to study high mountain disease, there was no way to anticipate the tremendous impact they would have on the study of high-altitude cardiopulmonary physiology. It was through the study of this agricultural malady that the correlation between chronic hypoxia, pulmonary hypertension, medial hypertrophy of the small pulmonary arteries, and right ventricular (RV) hypertrophy was recognized. The amount of vascular smooth muscle comprising the medial layer of pulmonary arteries varies significantly across species and can be used to predict the magnitude of pulmonary hypertension and RV hypertrophy elicited in response to chronic hypoxia. Within species, age and gender both significantly influence the severity of chronic hypoxic pulmonary hypertension and RV hypertrophy. However, despite all that we now know about hypoxic pulmonary hypertension, the specific mechanism(s) that differentiate the hypo- from the hyperresponder have yet to be elucidated. Adventitial fibroblast differentiation, circulating vascular progenitor cells, the presence or absence of specific vascular smooth muscle phenotypes, the upregulation or downregulation of vasoactive mediators, splice variants of oxygen-sensitive transcription factors, upregulation of growth factors, Ca2+ sensitization, and/or the Rho/Rho-kinases signaling cascade could all potentially play a role in determining the extent of the vascular response to hypoxia within a species. Understanding the mechanisms that determine why some people, as well as some animals, exhibit a marked susceptibility to hypoxia is an important endeavor with far-reaching implications.

Norepinephrine and dobutamine improve cardiac index equally by supporting opposite sides of the heart in an experimental model of chronic pulmonary hypertension

2021 ◽  
Author(s):  
Janus Adler Hyldebrandt ◽  
Nikolaj Bøgh ◽  
Camilla Omann Christensen ◽  
Peter Agger
Keyword(s):  
Pulmonary Hypertension ◽  
Cardiac Index ◽  
Pulmonary Artery ◽  
Right Ventricular ◽  
Left Ventricular ◽  
Ventricular Contractility ◽  
End Diastolic Volume ◽  
Chronic Pulmonary Hypertension ◽  
Blood Pressures ◽  
The Right

Abstract Background: Pulmonary hypertension is a significant risk factor in patients undergoing surgery. The combined effects of general anaesthesia and positive pressure ventilation can aggravate this condition and cause increased pulmonary blood pressures, reduced systemic blood pressures and ventricular contractility. Although perioperative use of inotropic support or vasopressors is almost mandatory for these patients, preference is disputed. In this study, we investigated the effects of norepinephrine and dobutamine and their ability to improve the arterio-ventricular relationship and haemodynamics in pigs suffering from chronic pulmonary hypertension.Method: Pulmonary hypertension was induced in five pigs by banding the pulmonary artery at 2–3 weeks of age. Six pigs served as controls. After 16 weeks of pulmonary artery banding, the animals were re-examined under general anaesthesia using biventricular conductance catheters and a pulmonary artery catheter. After baseline measurements, the animals were exposed to both norepinephrine and dobutamine infusions in incremental doses, with a stabilizing period in between the infusions. The hypothesis of differences between norepinephrine and dobutamine with incremental doses was tested using repeated two-way ANOVA and Bonferroni multiple comparisons post-test. Results: At baseline, pulmonary artery banded animals had increased right ventricular pressure (+39%, p=0.04), lower cardiac index (-23% p=0.04), lower systolic blood pressure (-13%, p=0.02) and reduced left ventricular end-diastolic volume (-33%, p=0.02). When incremental doses of norepinephrine and dobutamine were administered, the right ventricular arterio-ventricular coupling was improved only by dobutamine (p<0.05). Norepinephrine increased both left ventricular end-diastolic volume and left ventricular contractility to a greater extent (p<0.05) in pulmonary artery banded animals. While the cardiac index was improved equally by norepinephrine and dobutamine treatments in pulmonary artery banded animals, norepinephrine had a significantly greater effect on mean arterial pressure (p<0.05) and diastolic arterial pressure (p<0.05).Conclusion: While norepinephrine and dobutamine improved cardiac index equally, it was obtained in different manners. Dobutamine significantly improved the right ventricular function and the arterio-ventricular coupling. Norepinephrine increased systemic resistance, thereby improving arterial pressures and left ventricular systolic function by maintaining left ventricular end-diastolic volume.

Functional and structural changes with hypoxia in pulmonary circulation of spontaneously hypertensive rats

1994 ◽  
Vol 77 (3) ◽  
pp. 1101-1107 ◽  
Author(s):  
S. P. Janssens ◽  
B. T. Thompson ◽  
C. R. Spence ◽  
C. A. Hales
Keyword(s):  
Pulmonary Hypertension ◽  
Arterial Pressure ◽  
Vascular Remodeling ◽  
Spontaneously Hypertensive Rats ◽  
Structural Changes ◽  
Chronic Hypoxia ◽  
Acute Hypoxia ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto

Chronic hypoxic pulmonary hypertension involves both vasoconstriction and vascular remodeling. Spontaneously hypertensive rats (SHR) have an increased systemic vascular resistance and a greater responsiveness to constricting stimuli. We hypothesized that, in contrast to age-matched normotensive Wistar-Kyoto rats (WKY), SHR also display spontaneous pulmonary hypertension in normoxia and increased vascular response to acute and chronic hypoxia. Baseline mean pulmonary arterial pressure (PAP) and total pulmonary resistance (TPR) were higher in SHR than in WKY. With acute hypoxia (10% O2 for 15 min), PAP increased to the same extent in SHR and WKY and cardiac output (CO) was unchanged in WKY but increased in SHR. Thus, the rise in PAP in the SHR might be accounted for by the rise in CO, as TPR did not rise, but not that in the WKY, as TPR increased. After 12 days in hypoxia (10% O2), mean arterial pressure was unchanged in WKY but decreased significantly in SHR without a change in CO. PAP increased by 59% in SHR and 54% in WKY when the rats were taken from the hypoxic chamber for 1 h. Acute hypoxic challenge caused a further increase in PAP only in WKY. Medial wall thickness of alveolar duct and terminal bronchial vessels was similar in WKY and SHR after chronic hypoxia. We conclude that SHR exhibit mild baseline pulmonary hypertension in normoxia and that chronic hypoxia does not produce a disproportionate increase in SHR pulmonary vascular remodeling and pulmonary hypertension.

Secretory leukoprotease inhibitor attenuates lung injury induced by continuous air embolization into sheep

1995 ◽  
Vol 79 (4) ◽  
pp. 1163-1172 ◽  
Author(s):  
J. R. Gossage ◽  
E. A. Perkett ◽  
J. M. Davidson ◽  
B. C. Starcher ◽  
D. Carmichael ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Neutrophil Elastase ◽  
Serine Proteases ◽  
Structural Changes ◽  
Pulmonary Arteries ◽  
Neutrophil Elastase Inhibitor ◽  
Elastase Inhibitor ◽  
Arterial Circulation ◽  
Chronic Pulmonary Hypertension ◽  
Lung Lymph

Continuous air embolization (CAE) into the pulmonary arterial circulation of sheep results in functional and structural changes of chronic pulmonary hypertension. Release of elastin peptides into lung lymph during CAE and attenuation of CAE-induced pulmonary hypertension by neutrophil depletion suggest that neutrophil elastase may contribute to these changes. To investigate this notion, we treated awake sheep with a potent neutrophil elastase inhibitor, recombinant secretory leukoprotease inhibitor (SLPI) (100 mg/day by aerosol), during 12 days of CAE (CAE+SLPI; n = 7). Controls included sheep receiving CAE + vehicle (VEH) (n = 6), VEH alone (n = 3), and SLPI alone (n = 3). SLPI significantly attenuated the CAE-induced increases in lung lymph flow (day 8; 2.3 +/- 0.5 vs. 5.6 +/- 1.7 ml/15 min), protein clearance (day 8; 1.36 +/- 0.32 vs. 3.08 +/- 0.84 ml/15 min), and elastin peptide concentration (day 8; 243 +/- 41 vs. 398 +/- 44 ng/ml). SLPI delayed the onset of sustained pulmonary hypertension from day 8 to day 12. Both CAE groups showed similar structural changes in the pulmonary arteries. SLPI was well tolerated in control sheep and did not affect hemodynamics or structure. We conclude that serine proteases may contribute to the early initiation of chronic pulmonary hypertension but do not play a striking role in its eventual development.

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