Prostaglandin E₂ in Previtellogeic Ovaries of the Prawn Macrobrachium rosenbergii: Synthesis and Effect on the Level of cAMP

Elcosanoids are thought to play a role in the regulation of invertebrate reproduction, as they do in vertebrate systems. This was investigated using the previtellogenic ovary of the freshwater prawn Macyobrachium rosenbergii as a biological model. Concentrations of prostaglandin E₂ (PGE₂), assessed by means of radioimmunoassay, in the previtellogenic ovary (oocyte diameter 20-40 μm) were 32.4 ± 14.1 pg/mg ovary. Preincubation of the ovary with indomethacin (10 μM) inhibited PGE₂ synthesis by 43%. In addition, if indomethacin was added to the culture medium. cAMP levels decreased by 48%. When previtellogenic ovaries were incubated in vitro with PGE₂ (0.05 μg/ml medium and up), cAMP levels in the tissue homogenate sharply increased. The levels of cAMP rose most significantly (up to 10-fold) when 1-10 μg PGE₂/ml medium was applied. These results suggest that PGE₂, and possibly other prostaglandins, may play a role in the endocrine regulation of crustacean reproduction.