Interspecies Comparison of Phagolysosomal pH in Alveolar Macrophages

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Abstract
Differences in the translocation of dissolved particle mass from the lungs to the blood were found in a recent large interspecies comparison of long-term lung clearance after inhalation of uniform 57Co3O4 particles. Since the particles were dissolved most prominently in phagolysosornes of alveolar macrophages, the differences may have been due to differences in pH in these vacuoles. The phagolysosomal pH was measured in alveolar macrophages obtained by bronchoalveolar lavage from baboons, dogs, guinea pigs, and rabbits using fluorescein-labeled amorphous silica particles as a probe. In the alveolar macrophages from the 4 species pH was on average 4.8 or 4.9 with small variations among and within animals. The results indicate that it is unlikely that differences in phagolysosomal pH are responsible for the differences in translocation observed previously.