Studies of the mechanism of histamine release from lung tissue in vitro by cotton dust extracts.

Abstract

Using an in vitro incubation technique with human and pig lung, the histamine releasing activity of cotton dust extracts was examined. For both species, histamine release increased with increasing concentration of cotton dust in the medium. The maximum release obtained was about 26 and 15% for human and pig lung respectively at a concentration of 150 mg dust/ml and activity was optimal at 37°C. For human lung, there was a pH optimum for release at 7.4 but with pig lung this pH optimum was observed only at low concentrations of dust. Histamine release increased with increasing pH when pig lung was incubated with a high dust concentration (83 mg/ml). A Ca2+/Mg2+-free medium inhibited the release of histamine by cotton dust from pig lung. In the absence of glucose, potassium cyanide inhibited the release of histamine by dust from both human and pig lung. However, in the latter species, cyanide potentiated the effect of high dust concentrations. In pig lung, the histamine releasing activity of cotton dust was inhibited by 2,4-dinitrophenol (in a glucose-free medium), ninhydrin and N-ethylmaleimide. It is concluded that the release of histamine from lung tissue in vitro by cotton dust is due largely to an energy-dependent mechanism. However, at a dust concentration of 83 mg/ml, and particularly at an alkaline pH an energy-independent mechanism may also operate in pig lung. The results are discussed in relation to the occupational pulmonary disease, byssinosis.