Lead administered to laboratory rats in drinking water (0.1-0.8 %) as lead acetate solution tends to accumulate in collagen-rich tissues such as tendons and the skin. The amount of lead deposited (and also zinc present in the tissue without its supplementation) correlates with the blood supply to the tissue investigated. The highest deposits of lead were observed in placenta and chorionic membranes, though here only about 60% are collagen-bound. No differences in the drinking habits of the animals were observed and also at lower concentrations of lead in the drinking water no dose dependence was revealed. However, at 0.8 % of lead in drinking water considerable accumulation of lead was observed in all tissues investigated.
Pneumonia was induced in rats by instillation of carrageenin (0.5 ml of 0.7 % solution) into the trachea. Three or four days after instillation, the lungs were isolated, perfused with blood of healthy rat blood donors, and ventilated with air + 5 % C02 or with various hypoxic gas mixtures. Pulmonary vascular reactivity to acute hypoxic challenges was significantly lower in lungs of rats with pneumonia than in lungs of controls. The relationship between 02 concentration in the inspired gas and Po2 in the blood effluent from the preparation was shifted significantly to lower Po2 in lungs with pneumonia compared to control ones. These changes were not present in rats allowed to recover for 2- 3 weeks after carrageenin instillation. We suppose that blunted hypoxic pulmonary vasoconstriction may contribute to hypoxaemia during acute pulmonary inflammation. Decreased Po2 in the blood effluent from the isolated lungs with pneumonia implies significant increase of oxygen consumption by the cells involved in the inflammatory process.
Adult rats born in hypoxia but raised in air are more reactive to acute hypoxic challenges. The relation between perfusion pressure and perfusion flow (P/Q plot) was analyzed in the preparation of ventilated perfused lungs isolated from 3 groups of adult rats. Control animals of the first group were born and lived in air, the second group was born in hypoxic chamber and then the rats were raised in air. Rats of the third group were bom in air and exposed to hypoxia in adulthood. The P/Q plot in rats born in hypoxia had lower slope than that in controls. Acute hypoxia in control group resulted in parallel shift of P/Q line to higher pressures. In rats born in hypoxia, however, both intercept with pressure axis and slope were increased. This may be explained by the participation of both collapsible and non-collapsible parts of pulmonary vascular bed in hypoxic pulmonary vasoconstriction. Analysis of distribution of pulmonary vascular resistances by the double occlusion technique confirmed this possibility. In rats born in hypoxia both arterial and middle vascular segment resistances increased during acute hypoxic challenge. In control rats, however, the increase in resistance was restricted to the middle segment only.
We have studied in vitro alveolar macrophages (AMs) obtained by tracheobronchial lavage from rats exposed to subacute (3 hours and 3 days) and chronic (3 weeks) hypoxia (Fi02 = 0.1) and from rats recovering from chronic hypoxia. Hydrogen peroxide production by AMs was measured by luminol- depcndent chemiluminescence after AMs adhered to the walls of the measuring cuvette, after stimulation with phorbol-myristate-acetate (PMA), and when N-formyl-methionyl-leucyl-phenylanine (FMLP) was added subsequently to the cells which had been previously stimulated by adherence or PMA. H2O2 production after cell adherence and adherence combined with FMLP stimulation did not differ between the groups. The increase of H2O2 production after adding PMA, and FMLP in addition to PMA was significantly higher in AMs from rats exposed to hypoxia for 3 days than in the controls. Other experimental groups did not differ from their controls. It is concluded that 3 days’ hypoxia primes AMs for enhanced production of H2O2 upon stimulation. The mechanism is probably at the level of synthesis of proteins involved in H2O2 production, or the shift to a more reactive phenotype of alveolar macrophages subpopulations.
Production of hydrogen peroxide by rat lung alveolar macrophages represents one of the key events in the inflammatory process. For the interpretation of the in vitro measurements it is important to control all possible interfering influences. The present work documents that the type of anaesthesia might critically influence the observed results. H2O2 production was measured in isolated rat alveolar macrophages by luminol chemiluminescence catalyzed by horseradish peroxidase. Three different mechanisms of H2O2 production were observed after stimulation of cells with a chemotactic peptide (FMLP), phorbol ester (PMA), and during cell adherence. All these activities were influenced independently by the treatment with barbiturates, which both stimulated or inhibited the H2O2 production, depending on the barbiturate concentration. As the effective barbiturate concentrations were found to be within the range used for the anaesthesia of experimental animals, the presented results imply that barbiturates are not suitable for experiments in which the production of reactive oxygen species by phagocytes is measured, and that other anaesthetics should be tested.
Acute lung injury was induced by intravenous injection of 20 //I of a mixture of equivalent volumes of capronic acid, caprilic acid and olive oil in intact anaesthetized rats and in isolated perfused rat lung preparations. Lung injury in intact rats resulted in an increase in lung weight related to body weight and in a decrease in the lung dry/wet weight ratio. Lung compliance, measured in a body plethysmograph, was decreased. Pao2 decreased and Pac02 increased in 10 and 20 min, respectively, after the beginning of the experiment. Mean blood pressure in pulmonary artery increased immediately after the injection. Isolated rat lungs were perfused at constant flow with physiological saline solution containing bovine albumin and meclofenamate. The injection of a mixture of capronic acid, caprilic acid and olive oil increased the baseline perfusion pressure and led to a release of endothelial cells into the perfusate. The perfusion flow-pressure relationship was shifted upwards. Both the extrapolated pressure axis, intercept and slope of the plot were significantly elevated. The described experimental lung injury is a suitable model for studies on the effects of vascular wall damage and transvascular fluid leak in pulmonary vasculature.
Hydrogen peroxide injected into the inflow cannula of isolated ventilated rat lungs produced a dose-dependent vasoconstriction in the range 0.25-10 mM, with maximum response between 2 - 5 mM. The effects of H2O2 can be influenced by ionophores or specific inhibitors of ionic channels or pumps. A key role is played by sodium ions which govern the subsequent inflow or outflow of calcium, an ion mediating the vasoconstriction. A physiological role for H2O2 generated by NADPH oxidase is postulated.
The effect of chronic administration of angiotensin converting enzyme inhibitor on the development of hypoxic pulmonary hypertension was studied in rats. Male Wistar rats were exposed for 3 weeks to isobaric hypoxia (10 % O2) and treated with 10 mg/kg b.w. of Ramipril daily. The haemodynamic properties of the pulmonary vasculature were then measured in isolated blood-perfused lung preparation. Ramipril administration during the sojourn in hypoxia resulted in lower baseline perfusion pressure and lower slope of perfusion pressure-flow relationship compared to non-treated hypoxic rats. Partitioning of the distribution of pulmonary vascular resistance across the vascular bed by the occlusion technique showed that it was mainly due to a decrease of arterial and venous vascular resistances to blood flow. It is suggested that Ramipril attenuates the process of morphological reconstruction of pulmonary vasculature by chronic hypoxia rather than the level of vascular smooth muscle tone.