In vivo quantitation of epithelial lining fluid in dog lung

Development of a Sensitive High-Resolution Mass Spectrometry Approach for Urea Nitrogen Quantitation in Small Volumes of Bronchoalveolar Lavage Fluid (BALF)

A sensitive, selective, and quantitative method incorporating high-resolution mass spectrometry was developed for the determination of blood urea nitrogen (BUN) in bronchoalveolar lavage fluid. The method requires no sample cleanup or derivatization prior to analysis. High-performance liquid chromatography (HPLC) on a Hypersil Gold PFP column (100 × 3 mm, 3 μm particle size) connected to a C18 guard column was employed for a 10 min chromatographic separation. The detection of urea was achieved using a Thermo Scientific Q-Exactive Plus instrument incorporating selected ion monitoring (SIM) modes for the protonated adduct of urea. The urea analytical measuring range for the method is 0.047-17.134 mg/dL, resulting in a BUN analytical measurement range of 0.022-8.007 mg/dL, which allows for quantitation over 3 orders of magnitude (R² = 0.999). In addition, the method is suitable for small sample volumes (15 μL) with a high level of accuracy, precision, and specificity.

Biophysical activity of animal-derived exogenous surfactants mixed with rifampicin

Exogenous pulmonary surfactant is a potential delivery system for topical medications via the conducting airways. Due to the sensitivity to inactivation of surfactant, mutual interaction with the shipped drug should be evaluated. Little is known about the interactions between surfactant and antimicrobial drugs. The aim of the present study was to evaluate whether biophysical properties of animal-derived surfactants are modified by the bactericidal antibiotic rifampicin. An intracellular activity and a broad antimicrobiotic spectrum toward Gram-negative and Gram-positive bacteria make rifampicin an interesting substance against pulmonary infections. Curosurf® (porcine surfactant from minced lungs) and Survanta® (bovine surfactant extract) were diluted to 2.5-5.0 mg/ml of phospholipids in 0.9 % NaCl and rifampicin (RIF) was added at 1, 5, and 10 % (w/w). Minimum (γ(min)) and maximum (γ(max)) surface tension of a cyclically compressed bubble in the mixture was assessed with a pulsating bubble surfactometer. After 5 min, γ(min) of Survanta at a concentration of 3 mg/ml was significantly increased after addition of 5 and 10 % RIF (both p < 0.001). At 1 % RIF, the γ(min) of Survanta was ≈10 mN/m and this value was not significantly different to that of Survanta alone. The γ(min) of Curosurf at 3 mg/ml was increased with 10 % RIF (p < 0.001), but not with 1 and 5 %. At 5 mg/ml Survanta was inhibited by 10 % RIF (p < 0.05), while γ(min) of Curosurf was low (<5 mN/m) in all mixtures. In conclusion, Curosurf and Survanta interfere with RIF in a concentration-dependent manner. At the appropriate phospholipid concentration, especially porcine-derived surfactant is able to retain good surface activity when mixed with antibiotics.

Red blood cells prevent inhibition of hypoxic pulmonary vasoconstriction by nitrite in isolated, perfused rat lungs

Nitrite reduction to nitric oxide (NO) may be potentiated by a nitrite reductase activity of deoxyHb and contribute to systemic hypoxic vasodilation. The effect of nitrite on the pulmonary circulation has not been well characterized. We explored the effect of nitrite on hypoxic pulmonary vasoconstriction (HPV) and the role of the red blood cell (RBC) in nitrite reduction and nitrite-mediated vasodilation. As to method, isolated rat lungs were perfused with buffer, or buffer with RBCs, and subjected to repeated hypoxic challenges, with or without nitrite. As a result, in buffer-perfused lungs, HPV was reduced at nitrite concentrations of 7 muM and above. Nitrite inhibition of HPV was prevented by excess free Hb and RBCs, suggesting that vasodilation was mediated by free NO. Nitrite-inhibition of HPV was not potentiated by mild acidosis (pH = 7.2) or xanthine oxidase activity. RBCs at 15% but not 1% hematocrit prevented inhibition of HPV by nitrite (maximum nitrite concentration of approximately 35 muM) independent of perfusate Po(2). Degradation of nitrite was accelerated by hypoxia in the presence of RBCs but not during buffer perfusion. In conclusion, low micromolar concentrations of nitrite inhibit HPV in buffer-perfused lungs and when RBC concentration is subphysiological. This effect is lost when RBC concentration approaches physiological levels, despite enhanced nitrite degradation in the presence of RBCs. These data suggest that, although deoxyHb may generate NO from nitrite, insufficient NO escapes the RBC to cause vasodilation in the pulmonary circulation under the dynamic conditions of blood flow through the lungs and that RBCs are net scavengers of NO.

In vivo measurement of lung capillary-alveolar macromolecule permeability by saturation bronchoalveolar lavage

OBJECTIVE

Measurement of capillary-alveolar permeability to fluorescein isothiocyanate-dextran (FITC-D) (molecular mass, 71,300 daltons) by a sequential bronchoalveolar lavage (BAL) technique.

DESIGN

Animal research.

SETTING

The Department of Physiology at a scientific and medical university.

SUBJECTS

Nine anesthetized and mechanically ventilated dogs.

INTERVENTIONS

Two separate experiments were performed in each subject-an initial control experiment followed by an oleic acid-induced lung injury. The indicator was administered at constant blood concentration before serial BAL including eight fluid instillation-recovery cycles.

MEASUREMENTS

Plasma to BAL solute clearance at saturation (capillary-alveolar clearance at saturation, mL/min) was calculated and normalized to lavage fluid volume (measured by 1251 serum albumin dilution) to obtain a transport rate (TR) constant.

MAIN RESULTS

TR for FITC-D70 was 4.0+/-0.8 and 46.1+/-18.1 x 10(-5) x min(-1) in control and injured lung, respectively (p < .02). Capillary-alveolar clearance of FITC-D70 was not affected by the lavage procedure itself. TR reflected essentially epithelial permeability in normal lung and combined epithelial and endothelial permeability in injured lung. A significant correlation was found between cardiac output and TR in injured lung.

CONCLUSIONS

Saturation BAL allowed us to estimate capillary-alveolar macromolecule permeability in vivo in dogs. Further study may allow bedside evaluation of lung injury by BAL in patients.