Influence of 11-ketotestosterone, 17 beta-estradiol, and 3,5,3 '-triiodo-L-thyronine on distribution and metabolism of carotenoids in Arctic charr, Salvelinus alpinus L.

This investigation examines the influence of implants containing 11-ketotes tosterone (11KT), 17 beta-estradiol (E-2), and 3,5,3'-triiodo-L-thyronine ( T-3) on astaxanthin metabolism in sexually immature individually tagged Arc tic charr. The fish (initial average weight 427 g) were maintained in fresh water for 40 days, and weekly implanted intraperitoneally with oil-based in jections containing either 11 KT, E-2 or T-3 at levels of 0.1, 1.0 and 0.1 mg (100 g body weight (BW))(-1), respectively. The control fish were given the oil medium alone (0.2 ml 100 g BW-1). The diet contained ca. 50 mg asta xanthin kg(-1). Carotenoid composition was monitored in plasma, fillet, liv er and skin, and 11 KT, E-2 and testosterone (T) levels in plasma. All horm one treatments reduced plasma T compared to the control. E-2-treated fish h ad a higher (p < 0.05) hepatosomatic index (HSI) than the other treatments. Hormone treatment did not influence gonadosomatic index (GSI). T-3 adminis tration induced a silvery skin appearance. The fillet and plasma carotenoid content decreased during the experiment. 11 KT implantation reduced astaxa nthin and idoxanthin concentrations of plasma and fillets, and increased th e amount in liver and skin, compared to the other treatments. The relative proportion of astaxanthin to idoxanthin was higher in the control fish and T-3 implanted fish, than in fish implanted with 11 KT or E-2 (p < 0.05). Fi sh treated with E-2 had the highest skin carotenoid concentration. Male fis h had significantly higher carotenoid content in plasma, fillet and skin th an female fish. This study reveals that sex hormones affect carotenoid meta bolism and partitioning among body compartments of Arctic charr, effects di fferently displayed by the sexes.