Distribution of silicon in the adult rat and rhesus monkey

The distribution of silicon in tissues of the rat and rhesus monkey was determined using a colorimetric method specifically designed for biological materials. Soft-tissue silicon levels in both species varied from 1 to 33 mug silicon/g dry weight (ppm) excepting the primate lung and lymph nodes, which averaged 942 ppm and 101 ppm, respectively. This distribution may reflect flow-through of silicon in the form of particulates and water-soluble silicate contaminates in the environment and food effectively masking tissue or organ-specific silicon of functional significance. The silicon content of the whole rat femur was 38 ppm as determined by emission spectroscopy, whereas the monkey femur shaft was 43 ppm and the femur head containing the epiphysis was 456 ppm. This silicon may be functionally involved in the calcification process as suggested by others. The silicon content of rat liver subcellular fractions was also determined. The supernatant, nuclei/debris, and mitochondrial portions contained 0.6-1.0 mug silicon/g liver equivalents, whereas the microsomal fraction contained only 0.2 mug silicon/g liver equivalents.