Biochemical and morphological studies of human diploid and fluoride-resistant fibroblasts in vitro.

Fluoride-resistant (FR 30) lines were produced from human diploid fibroblast (NDU-1) cells by progressively increasing the concentration of fluoride (F) in the growth medium up to 1.58 mM. This concentration completely inhibited the growth of the original cells. The resistant cells had decreased incorporation of [14C]-leucine and an increased rate of the cell division. The activities of acid phosphatase, alkaline phosphatase, lactate dehydrogenase, leucine aminopeptidase, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and alpha-hydroxybutyrate dehydrogenase in the FR 30 cells were lower than in the NDU-1 cells. The FR 30 cells had irregular shapes and sizes; the amount of undeveloped rough endoplasmic reticulum and the number of lysosomes were increased. These biochemical and morphological changes in FR 30 cells suggest that their metabolic activities were depressed by F, although they have some degree of F resistance.