The lipoxygenase pathway of arachidonic acid metabolism in reproductive tissues of the firebrat, Thermobia domestica (Thysanura)

The reproductive tissues of the primitive insect Thermobia domestica synthesize several eicosanoids when incubated with exogenous arachidonic acid. The enzymatic system was characterized with respect to kinetic parameters, Ca²⁺ requirement and pH- and cofactor-dependence. Five monohydroxylated eicosatetraenoic acids (HETEs) were identified by mass spectrometry procedures, demonstrating the existence of the lipoxygenase pathway. Quantitative studies were performed by high-pressure liquid chromatography. It is confirmed that the 8-lipoxygenase activity remains the major pathway in tissues from males and from inseminated females. In female tissues, the amounts of metabolite depend on the number of spermatophores contained in the seminal receptacles. These data are in agreement with the hypothesis of a transfer of the enzyme from male to female during mating. The mechanisms involved are discussed in comparison with those of other insect species in which the synthesis of prostaglandins has been reported.