INCREASES IN 13-HYDROXYOCTADECADIENOIC ACID DEHYDROGENASE-ACTIVITY DURING DIFFERENTIATION OF CULTURED-CELLS

Recently, oxidation products of linoleic acid such as 13-hydroxyoctade cadienoic acid (HODE) have been implicated in the regulation of cellul ar physiology including the proliferative response to growth factor tr eatment. In addition, an NAD+-dependent 13-HODE dehydrogenase was rece ntly described. To evaluate the contribution of this enzyme to cellula r processes we have examined the behavior of the enzyme under differen t conditions. In the present report, changes in the activity of 13-hyd roxyoctadecadienoic acid dehydrogenase during in vitro differentiation of two different cell lines were examined. The cell line HT-29 underg oes induced differentiation via manipulation of the medium while the C aco-2 line undergoes spontaneous differentiation upon attainment of co nfluence. In both cell fines, longer culture times were accompanied by increases in 13-HODE dehydrogenase activity. The increase in enzyme a ctivity continued even after cell proliferation had ceased. Cellular d ifferentiation was verified by the observation of increases in sucrase and alkaline phosphatase activities. In addition, the activity of 13- HODE dehydrogenase was measured in growing, early confluent and late c onfluent cultures of undifferentiating Swiss mouse 3T3 fibroblasts. In the fibroblast tine, no significant changes in 13-HODE dehydrogenase activity were observed during the course of the experiment. The specif ic activity of 13-HODE dehydrogenase was also significantly different between the three cell tines, consistent with the extent of differenti ation. Highest levels of activity were found in Caco-2 cells (200-400 pmol/min/mg), intermediate levels in the HT-29 cells (20-60 pmol/min/m g) and barely detectable levels in the fibroblasts (0.6-2 pmol/min/mg) . The correlation between 13-HODE dehydrogenase and cell differentiati on suggests the enzyme may have a role to play in the partitioning of cells between proliferation and differentiation pathways.