Subcellular targets of the soluble SiO 2-liberated macrophage factors in experimental granulation tissue

Abstract

The supernatant from SiO 2-treated macrophages increased the incorporated radioactivity of collagen in the incubated experimental granulation tissue slices, especially in the rough endoplasmic reticulum fraction, markedly over that in the respective control preparation. The effect was observed after a 20 min incubation and increased linearly at least up to 3 h. The amount of RNA and phospholipids in the rough endoplasmic reticulum, calculated per protein, increased simultaneously in the incubated slices. The incorporation of the radioactive precursors into DNA in the slices and in the nuclei from proliferating granulation tissue was enhanced significantly by the soluble fraction from SiO 2-treated macrophages. This effect could be seen after a 40 min incubation in the slices and after 5 min in the nuclei, when the incorporated radioactivity in DNA began to decrease in the control experiments.