Effect of 13-hydroperoxyoctadecadienoic acid on 15-hydroxy prostaglandin dehydrogenase activity in rabbit kidney cortex

The effect of a hydroperoxy adduct of linoleic acid, 13-hydroperoxyoctadecadienoic acid (13-HPODE), on 15-hydroxy prostaglandin dehydrogenase activity in rabbit kidney cortex was examined. 13-HPODE inhibited the 15-hydroxy prostaglandin dehydrogenase activity at concentrations ranging from 1 to 10 microM. The effect was concentration-dependent and the concentration required for 50% inhibition was approximately 3 microM. Linoleic acid and 13-hydroxyoctadecadienoic acid (13-HODE) exhibited weaker inhibition of the enzyme activity than did 13-HPODE (linoleic acid, 30% inhibition at 10 microM; 13-HODE, 45% inhibition at 10 microM). Studies utilizing Fe2+ (a catalyst of peroxide decomposition), and mannitol or dimethylsulfoxide (a hydroxy radical scavenger) revealed that the inhibitory effect of 13-HPODE on the 15-hydroxy prostaglandin dehydrogenase activity is not due to the hydroxy radicals which are expected to be formed from 13-HPODE and that the hydroperoxy functional group is a prerequisite. The inhibition by 13-HPODE was uncompetitive and non-competitive with regard to NAD+ and prostaglandin E2, respectively. These results suggest that 13-HPODE has the potential to modulate the prostaglandin catabolism by affecting the 15-hydroxy prostaglandin dehydrogenase activity.