Blood samples were collected by cardiac puncture from trout,
anaesthetised in a solution of MS222 (tricaine methanesulfonate,
100 mg/l). Analysis for cholecalciferol and 7-dehydrocholesterol in
lipid extracts of trout tissues was performed by high performance
liquid chromatography (HPLC) according to standard methods [10].
Determination of 25-hydroxy-cholecalciferol [25(OH)D] or 1,25-
dihydroxycholecalciferol in lipid extracts was done either by
competitive protein binding assays or by HPLC [10]. HPLC analysis
of cholecalciferol had a minimum detection limit of 1 ng/g wet
tissue.