No abstract

Volume–pressure curves obtained from isolated atelectatic rat lungs under normal control conditions were compared with those obtained from lungs of animals previously exposed to inhalation of submicronic aluminum oxide particles for various periods of time. A dilating effect was recorded in rat lungs after aluminum oxide particle inhalation contrasting with the constricting effect reported by many authors in guinea pig, dog, cat, and man. Inhalation of fine aluminum particles before or after inhalation of sympathomimetic aerosol resulted in a more intense dilatation. The constricting effect of carbachol was antagonized by prior inhalation of fine aluminum oxide dust and enhanced when the order of inhalations was reversed.

In previous experiments, the inhalation of aluminum or iron oxide submicronic particles was shown to possess strong constricting properties, using the method of volume–pressure curves with atelectatic guinea pig lung. The constricting effect of aluminum was prevented by cyproheptadine, an antihistaminic and antiserotonin substance. In the present experiments, determinations of serotonin and histamine in dust-treated lungs were undertaken; the content of serotonin and of histamine was found to be increased after aluminum and after iron oxide particle inhalation respectively. Serotonin and histamine given as aerosols to guinea pigs reproduced the characteristic volume–pressure curves obtained after aluminum or iron oxide microparticle inhalation, respectively.

Volume–pressure curves obtained from isolated atelectatic guinea pig lungs under normal controlled conditions are compared with those obtained from animals having inhaled fine aluminum or iron oxide particles. After particles inhalation, the inflation curves are deviated to the right, showing a constricting effect. Previous exposure to low concentration of isoproterenol aerosol fails to reverse completely the constricting effect induced by a prior inhalation of aluminum oxide particles although in combination with diphenhydramine or at a higher concentration an antagonistic action appears. Cyproheptadine aerosolation also prevents the constricting effect of inhaled aluminum oxide particles The constricting effect of iron oxide was not prevented by those dilating aerosols at concentrations used.

Rats were exposed to an atmosphere containing submicronic aluminum oxide particles or to aerosols of carbachol or isoproterenol. The static pressure – volume curves of their lungs, rendered gas-free and removed after exposure, were then compared to those of normal rats studied similarly. The lungs were filled and emptied gradually both with air and with saline so that in every case the force due to tissue elasticity, as well as that due to the surface tension of the alveolar lining, could be determined. Carbachol aerosol (1%) inhalation for 7 minutes produced an increase in the force due to tissue elasticity. The inhalation of aluminum oxide particles, less than one micron in diameter, for half an hour also increased the force due to tissue elasticity slightly, but it greatly decreased the force due to the surface tension of the alveolar lining.