Growth-modulating effects of dichloro myristic and dichloro stearic acid in cell cultures

Chloro-containing fatty acids are a major fraction of extractable, organica lly bound chlorine in fish. It has been suggested that dichloro stearic aci d (9,10-dichlorooctadecanoic acid) (C18) is metabolized to dichloro myristi c acid (5,6-dichlorotetradecanoic acid) (C14) which accumulates in tissues. Hence, the biological effects of the C18 dichloro fatty acid could be due to formation of the C14 dichloro fatty acid. Ln this study we have compared the effects of dichloro stearic and dichloro myristic acid on growth of th ree widely differing cell lines. Both fatty acids inhibited cell growth; ho wever, dichloro myristic acid had a weaker growth inhibitory effect than di chloro stearic acid. Dichloro myristic acid had a biphasic effect (i.e. gro wth was stimulated at low concentrations, followed by inhibition at higher concentrations) on the growth of human hepatoma cells and immortalized huma n kidney epithelial cells, but no such effect on human microvascular endoth elial cells. The order of potency for growth inhibition by dichloro myristi c acid was consistently human hepatoma cells>immortalized human kidney epit helial cells >human microvascular endothelial cells, whereas the relative p otency of dichloro stearic acid was variable. Albumin alone stimulated cell growth and had a stronger protective effect against growth inhibition by d ichloro myristic acid than against that of dichloro stearic acid. It seems unlikely that a major part of the effect of dichloro stearic acid on cell g rowth is caused by conversion to dichloro myristic acid.