Source of alkaline phosphatase activity in epithelial lining fluid of normal and injured F344 rat lungs.

In pulmonary toxicity screening tests in which the epithelial lining fluid (ELF) is sampled by bronchoalveolar lavage (BAL), investigators have observed both increases and decreases in alkaline phosphatase (AP) activity in BAL fluid during an acute inflammatory response. Such alterations in AP activity are difficult to interpret because of uncertainties concerning the source of the AP. It could be coming from type II cells, or from influxing neutrophils or serum, along with transudation of proteins due to the increased permeability of the alveolar capillary barrier. To aid in determining the source of AP activity in ELF during an acute inflammatory response, AP in ELF from control F344 rats was compared to AP in ELF from endotoxin-treated or quartz-treated rats and to AP in serum, type II cells, neutrophils, and lungs of untreated rats. The isoelectric focusing pattern and the inhibition by amino acids, a chelating agent, and heat were used to characterize the AP from the different sources. The AP in ELF from control and from inflamed lungs had similar characteristics and closely resembled AP in type II cells, total lung, and neutrophils. It was concluded that type II cells, and not neutrophils, were the major source of AP in ELF for two reasons: (1) The amount of AP activity in neutrophils was approximately 40-fold less than in type II cells, and (2) earlier studies indicated an enhanced increase in AP activity in ELF in neutrophil-depleted versus nondepleted rats in response to alpha-quartz. Current evidence from this study and others suggests that AP in ELF is associated with secreted surfactant, indicating that alterations in ELF levels of AP may mean changes in the rate of surfactant secretion or turnover. Time course studies on the alterations in AP activity in ELF in relation to histopathological changes in alveolar epithelia and surfactant secretion are needed to further interpret the significance of AP activity in ELF.

Biological markers of exposure to SO2: S-sulfonates in nasal lavage.

S-sulfonate levels were measured in the nasal lavage (NAL) fluid of humans exposed to sulfur dioxide as a potential biological marker of exposure. These levels were determined by treating NAL fluid protein with cyanide to cleave the S-S linkage and release the sulfite. The cyanolytically released sulfite was measured by ion chromatography. In two experiments, humans were exposed to air or 1 ppm SO2 for 10 minute, and to air or 7 ppm SO2 for 20 minutes and lavaged immediately after exposure. Releasable sulfite levels in NAL fluid were 1.06 +/- 0.24 and 2.61 +/- 0.55 micrograms SO=3/mg protein, respectively (mean +/- SE, n = 5), for the first experiment, and 1.16 +/- 0.37 and 4.91 +/- 0.76 micrograms SO=3/mg protein, respectively (mean +/- SE, n = 8), for the second. The subjects in the former study were persons with asthma. In both experiments, S-sulfonate levels were statistically elevated in the exposed group compared with the control groups (p < 0.05, paired t-test). The same individuals in the second experiment received five additional 20-minute exposures to 7 ppm SO2 every other day, for a total of six exposures. NAL fluid taken at the conclusion of the final exposure had releasable sulfite levels of 4.99 +/- 1.36 micrograms SO=3/mg protein; these levels were statistically elevated relative to controls but were not elevated relative to the 1-day exposure (mean +/- SE, n = 8). The lack of accumulation of S-sulfonates after 6 days of short-term exposure suggests clearance of these compounds from the nasal passages within 24 hours. The levels of S-sulfonates observed in NAL fluid in this study are almost three orders of magnitude higher than those measured in plasma following similar SO2 exposures. Measurement of S-sulfonates in the nasal passage may be an effective short-term biomarker of exposure to SO2.

A rapid method for determining soot content of lungs in diesel-exposed rodents.

A rapid optical method for determining the quantity of soot in the lungs of rodents exposed to diluted diesel exhaust has been developed. The method is nondestructive to enzymatic components of the lung, allowing dose and biochemical assays to be done on the same sample. The lung burdens of soot were determined by comparing the extinction of light at 620 nm of lung homogenates from exposed animals to that of lung homogenates containing spiked standards.

Replacement time for alveolar lipid removed by pulmonary lavage: effects of multiple lavage on lung lipids.

Daily washing in vivo of the lung with 0.15 M saline did not deplete the Beagle dog lung of surfactant lipids, but rather increased the quantity of surfactant lipid in the tissue. Replacement time for the lung lipids removed by the lavage was approximately 5 hours. This rate is one indication of the time required for movement of surfactant lipid from storage areas to the surface of the alveoli. The increase in tissue surfactant lipid following multiple lavage suggests that the rate of surfactant lipid synthesis is controlled in part by the level of surfactant lipid in the alveoli.