Abstract

Tissue cultures of fibrogenic cells which form collagen in vitro are a valuable model for quantitative study of the mechanism of this cellular function as well as of problems relevant to pneumoconiosis. We have found a pronounced stimulation of collagen formation in tissue cultures of embryonic chicken lung by silicic acid in a concentration of 0·005M in the medium. Higher concentrations (0·01 M) were inhibitory as were quartz dust particles of 50 to 70 mg. per culture tube, which, during the eight days of incubation, liberated silicic acid in concentrations of an inhibitory order into the culture medium. A low concentration (0·001 M) of silicic acid or of silica dust (5 mg.) was ineffectual as was an inert dust (TiO₂) in a high concentration (50 mg.). Evidence is presented that the stimulatory effect of silicic acid is due to a direct stimulation of postulated enzymatic systems taking part in fibrogenesis. Estimation of dioxyribonucleic acid in the cultures indicated that the number of cells was similar in controls and in cultures with increased and reduced collagen content.