Development of hemolymph prostaglandins assay systems and their concentration variations during ovarian maturation in the kuruma prawn, Penaeus japonicus

Hemolymph prostaglandin (PGF(2alpha) and PGE(2)) measurement systems for the kuruma prawn Penaeus japonicus were developed and validated. In these systems, both PGF(2alpha) and PGE(2) in hemolymph obtained from a single prawn were measured. PGs were extracted through reverse-phase C 18 cartridge column, separated for isomers of each PG by high-performance liquid chromatography (HPLC), and quantified with a radioimmunoassay (RIA). Detectable range was 6.5-200 and 26-400 pg/tube for the PGF(2alpha) and PGE(2) assays, respectively. Serial dilution of extracted and separated hemolymph PGs (RIA sample) produced a curve parallel to the standard curves in both assays. These assays were able to measure PGs in the RIA samples spiked with the authentic standard. Overall, results indicate that the presently established assay systems can accurately measure hemolymph PGs in female kuruma prawns. When hemolymph PGF(2alpha) and PGE(2) levels were determined and plotted against the gonado-somatic index (GSI), no correlation was found in either PGs. In terms of ovarian developmental stages, however, the concentration of PGF(2alpha) significantly increased from 66.7 pg/ml at stage I (previtellogenic stage) to 303 pg/ml at stage II (primary vitellogenic stage) and decreased gradually thereafter. The concentration of PGE(2) also increased markedly (4037.7 pg/ml) at stage II and decreased at stage III (secondary vitellogenesis stage). These results indicate that PGs vary in concentration during ovarian development in kuruma prawns. (C) 2003 Elsevier Science B.V. All rights reserved.