Effect of fluoride on the activity of ornithine decarboxylase in normal and fluoride resistant LS cells.

Renewal of growth medium caused an induction of ornithine decarboxylase (ODC) activity in LS cells grown in suspension culture. Addition of low concentrations of fluoride ions to the growth medium (up to 1.3 mM) resulted in a further increase in this induction of ODC-activity, whereas addition of 6 mM fluoride caused an inhibition of the induction and resulted in reduced ODC-activity as compared to controls. Since sodium fluoride had no stimulatory or inhibitory effect on the ODC-activity assay, it is likely that the effect is exerted on the regulation of ODC-activity in the cells. The effect of fluoride ions on the induction of ODC-activity upon renewal of the growth medium was markedly less pronounced in fluoride resistant LS cells.