Objective Ultrastructural changes in epithelial cells of livers, adrenal glands, and thyroid glands of human fetuses from a fluorosis-endemic area were observed to provide an experimental basis for investigating the mechanism by which fluoride causes cellular damage.
Methods 10 human fetuses in a fluorosis-endemic area were collected, whose mothers all had dental fluorosis with urinary fluoride content of (4.37 ± 2.94) mg/L. 10 human fetuses in a non-fluorosis-endemic area were collected, whose mothers had no dental fluorosis with urinary fluoride content of (1.67 ± 0.82) mg/L. The fluoride electrode method was used to test the fluoride content in fetal bones. Tissues of livers, adrenal glands, and thyroid glands of the fetuses were taken for electron microscopic examinations.
Results The fluoride content in bones of the fetuses in the endemic area was (2.77 ± 0.25) mg/kg; compared with the fluoride content in bones of fetuses in the non-endemic area of (2.50 ± 0.11) mg/kg, the differences are significant (P < 0.01). Electron microscopic examinations showed: the major changes of cell membranes were microvilli that were shortened, reduced in number or even vanished. Intercellular connections were loose and their structure was disordered. Myelin-like structures were formed in those with severe pathological changes. The major mitochondrial changes were: swollen mitochondria with increased volume, and even vanished and vacuolated cristae. The major pathological changes of endoplasmic reticulum were dilated and vesicular rough endoplasmic reticulum, and partially depleted nucleoproteins on the rough endoplasmic reticulum. The major pathological changes of cell nuclei were damaged and dilated, vesicular dual-layer structures of nuclear membranes. Huge inclusion bodies or particles with relatively high abnormal electron density appeared in some cytoplasm.
Conclusions Fluoride damage to cell structures was multifaceted. Cell membranes, mitochondria, rough endoplasmic reticulum, and nuclear membranes could all be damaged at the time of fluorosis.