Tissue uptake of radioactive cholesterol in the prawnPenaeus japonicus Bate during induced ovarian maturation

Abstract

The in vivo distribution and fate of ¹⁴C-cholesterol injected in prepuberal female prawns, Penaeus japonicus Bate, intact (E⁺) or deprived of their eyestalks (E⁻), were investigated. Animals were injected at the beginning of the experiment. Three days later, half of them (24 specimens) supported bilateral eyestalks ablation within a 48 hours period. Four days after the ablation, the ovaries of eyestalkless animals were relatively more developed than those of intact animals as seen by the increase in ovarian weight. The total content ¹⁴C-cholesterol and/or its metabolic products (total dpm) in whole animals was not significantly different between the two lots of animals and remained nearly constant throughout the experiment.

Distribution of radioactivity (dpm/mg wet weight of tissue) in carcass, muscle, gut, hepatopancreas,eyes and eyestalks and ovaries from E⁺ and E⁻ after 192 hours of ¹⁴C-cholesterol injection indicate that ovaries presented the highest concentration of label (6 to 40 times higher than other organs) while these differences were not statistically significant between E⁺ and E⁻. The study of incorporation of ¹⁴C-cholesterol in those organs from E⁺ and E⁻ independent of their volume, expressed as percentage organ radioactivity/whole animal radioactivity, at different time points, indicate that major accumulation was achieved by the carcass and muscle although radioactivity in the muscle progressively increased in inverse correlation with the decrease observed in the carcass. Hepatopanereas, eyes and eyestalks, gut and ovaries showed small incorporation that was kept constant with time in eyes and guts and significantly decreased in ovaries and hepatopancreas. At 192 hours after ¹⁴C-cholesterol injection there was an apparent increase in ¹⁴C label retention in ovaries from E⁻ compared to E⁺ that was not statistically significant.

Results indicate that the ovary is presumably the major site of cholesterol metabolism followed bythe hepatopancreas. Muscle seemingly is the major site for storage of large amounts of cholesteroland/or its metabolites while eyes and gut have negligeable retention. Furthermore, in our experimental conditions, the requirement for cholesterol in different tissues does not vary significantly with eyestalk ablation suggesting that the phenomenon could be independent of ovarian maturation and moulting.