Biweekly patterns of change in food consumption, plasma thyroid hormone and growth hormone levels, andin vitrohepatic monodeiodination of T4 in rainbow trout,oncorhynchus mykiss

Effect of recombinant human GH and GHRH on plasma metabolite levels in rainbow trout (Oncorhynchus mykiss)

The aim of the present work was to study metabolic changes in rainbow trout treated with preparations of human recombinants of growth hormone (rhGH) and GH-releasing hormone (rhGHRH), by analysing time course variations in plasma metabolite levels. Trouts were given the hormones by intraperitoneal injection in a single dose (rhGH: 0.5microg/g b.w.; rhGHRH: 0.06microg/g b.w.) or as a weekly injection over a period of 4 weeks. The concentrations of glucose, lactate, free fatty acids and glycerol were determined in plasma immediately before injection and 1, 3, 6, 12, 24, 48 and 168 hours post-injection. Results indicate that glucose and lactate levels increase, while slight variations in free fatty acids was observed after the injection of rhGH and rhGHRH.

Optical quality changes of the ocular lens during induced parr-to-smolt metamorphosis in Rainbow Trout (Oncorhynchus mykiss). Ocular lens optical quality during induced salmonid metamorphosis

The effect of an induced salmonid parr-to-smolt metamorphosis ('smoltification') on the optical quality of the ocular lens was studied. In two separate experiments, rainbow trout (Oncorhynchus mykiss) parr were fed thyroxine in their diet to induce the metamorphosis. Lenses were excised at regular samplings during the treatment period and optically scanned using a custom scanning laser monitor. Radioimmunoassay was used to measure serum titers of thyroxine and 3,5,3'-triiodo-L: -thyronine. It was found that lens optical quality was consistently negatively correlated with 3,5,3'-triiodo-L: -thyronine levels, but not with thyroxine levels. To test if thyroid hormones are directly responsible for the change in optical quality, rainbow trout lenses were cultured for 72 h in a medium containing 3,5,3'-triiodo-L: -thyronine, but no effect was observed. The significance of these findings in the contexts of the fishes' visual capabilities and smolting physiology is discussed.