Experimental Silicosis: The Inhibitory Effect of Iron

Abstract

The inhibition of the fibrogenic action of quartz dust by associated iron, initially reported by Kettle and later confirmed by Gardner and Vorwald has been reconfirmed. In rats, this inhibition was temporary, serving to delay the maturation of silicotic nodules by a few months only. In guinea pigs, iron completely prevented the formation of silicotic nodules but it did not inhibit completely the development of collagen within thickened alveolar walls. In rats, the development of collagen within silicotic nodules paralleled the disappearance of iron from these sites. In guinea pigs, the iron had also disappeared from those regions in which collagen had developed. Yet, there were other foci in which there was manifest inhibition of collagen formation in spite of the fact that abundant iron-free silica was demonstrable in such regions. This apparent inhibition of fibrosis in the absence of iron contradicts Gardner’s premise (applied to aluminum) that the inhibiting substance, to be effective, must occupy the same cell as the quartz particle which it inhibits.