Lack of haemodynamic effects of nitric oxide on post-capillary pulmonary hypertension induced by acute sino-aortic denervation

GREATER HYPERTROPHY IN RIGHT THAN LEFT VENTRICLES IS ASSOCIATED WITH PULMONARY VASCULOPATHY IN SINOAORTIC-DENERVATED WISTAR-KYOTO RATS

1. Biventricular hypertrophy has been described in a high blood pressure variability (BPV) model of sinoaortic-denervated (SAD) rats without systemic hypertension. To explore the possible involvement of the lung in SAD-induced right ventricular hypertrophy (RVH), we examined lung morphology, in addition to systemic haemodynamics and ventricle morphology, in Wistar-Kyoto rats 32 weeks after SAD. 2. In Wistar-Kyoto rats 32 weeks after SAD, there existed a substantial elevation in BPV, with no change in the average level of arterial pressure. Biventricular hypertrophy following SAD was characterized by a greater hypertrophy in right than left ventricles; both absolute and normalized right ventricular weights were significantly increased by 22 and 27%, respectively, and only normalized left ventricular weight was significantly increased by 12%. No infarcts were found in any ventricles examined. 3. In the lung, the most prominent change following SAD was pulmonary vasculopathy, including wall thickening, perivascular fibrosis and cell infiltration. In pulmonary arteries with an internal diameter of 70-130 microm, the external diameter, wall thickness and wall thickness to internal diameter ratio were increased in SAD compared with control rats. 4. There was no correlation between right and left ventricular weights. In contrast with BPV-correlated left ventricular weight, right ventricular weight was correlated with the wall thickness of the pulmonary artery, but not with BPV. 5. These findings suggest that greater RVH following SAD is associated with pulmonary vasculopathy, but is not secondary to the left ventricular problems or high BPV.

Nitric oxide (NO) modulation of PAF-induced cardiopulmonary action: interaction between NO synthase and cyclo-oxygenase-2 pathways

1. To further investigate into the mechanisms of PAF-induced cardiopulmonary actions, we examined the effects of the nitric oxide synthase (NOS) inhibitor L-N(omega)-nitro-L-arginine (L-NNA), of the specific cyclooxygenase-2 (COX-2) inhibitor NS 398, and of the combined presence of both COX and NOS inhibitors on the PAF responses in the heart lung preparation of guinea-pig (HLP). 2. In HLPs perfused with homologous blood, dose-response curves for the haemodynamic and bronchial effects of PAF (1 - 32 ng) were carried out in the absence or presence of L-NNA (200 microM). L-NNA caused an increase in the resting pulmonary arterial pressure (PAP) without affecting the other basal values, and strongly potentiated the bronchoconstriction and pulmonary hypertension elicited by PAF. An enhancement of the PAF-induced actions on right atrial pressure (RAP) and cardiac output (CO) was also observed. All the effects of L-NNA were antagonized by L-arginine (2 mM). 3. The presence of L-NNA in the perfusing blood of HLPs failed to affect the pulmonary hypertensive and bronchoconstrictor responses induced by the thromboxane A(2) mimetic U46619 (0.05 - 1.6 microg), 5-hydroxytryptamine (0.1 - 1.6 microg), and histamine (0.1 - 1.6 microg), thus suggesting that these PAF secondary mediators are not responsible for the hyper-responsiveness to PAF induced by L-NNA. 4. Blocking COX-2 pathway with NS 398 (15 - 30 microM) did not alter the cardiopulmonary resting variables. However, a reduction of the PAF-mediated pulmonary hypertension, but not of bronchoconstriction, was observed. When L-NNA was added to the perfusing medium of HLPs pre-treated with NS 398 or with indomethacin (15 microM), the basal PAP values were enhanced. However, in the combined presence of COX and NOS inhibitors, only a slight increase in the hypertensive responses to the highest doses of PAF was observed, whereas the PAF mediated actions at bronchial and cardiac level were unaffected. 5. This study indicates that (i) the cardiopulmonary actions induced by PAF are specifically modulated by endogenous NO through the NOS pathway, and (ii) COX-2 isoform is involved in the pulmonary hypertensive, but not bronchoconstrictor, effects of PAF. Furthermore, an interaction between PAF stimulated COX, particularly COX-2, and NOS pathways appears to take a functional role at both bronchial and cardiovascular level.

Inhaled nitric oxide does not alter pulmonary or cardiac effects of fat embolism in dogs after cemented arthroplasty

PURPOSE

We examined the effect of inhaled nitric oxide (NO) on the acute pulmonary hypertension and right ventricular (RV) dilation after fat embolism.

METHODS

A bilateral cemented arthroplasty (BCA), created fat embolism in 20 dogs. In Part A, 12 dogs were randomized to an NO group (n=6, inhaled NO 40 ppm before BCA and throughout the study) or a control group (n=6). In Part B, a third group of dogs (n=8) were given NO 20-40 ppm 2-3 min after BCA when pulmonary artery pressure (PAP) increased. Transesophageal echocardiography (TEE) and invasive hemodynamic monitoring evaluated the hemodynamic response to BCA. Postmortem, quantitative morphometry was used to estimate the number of fat emboli and diameter of lung vessel occluded by fat.

RESULTS

Part A: The increase in PAP in the NO group (16 +/- 1 to 34 +/- 9 mmHg) within three minutes of BCA was not different from that in the control group (14 +/- 4 to 35 +/- 9 mmHg). Within three minutes of BCA, TEE demonstrated RV dilation in all groups (P < 0.05) but there was no difference in the change in RV area in the NO and control groups. When NO was given after BCA, no difference in PAP or RV dilation was noted from that in the control group. There were no differences, at post mortem, between the groups in the diameter of lung vessel occluded by fat

CONCLUSION

Whether given before the embolic insult or two to three minutes after the onset of pulmonary hypertension, inhaled NO did not attenuate the acute pulmonary hypertension or RV dilation after cemented arthroplasty.