Hepatic ascorbic acid saturation is the most stringent response criterion for determining the vitamin C requirement of juvenile European sea bass (Dicentrarchus labrax).

Our main objective was to verify whether the dietary ascorbic acid (AA) requirement of juvenile European sea bass (Dicentrarchus labrax) varies as a function of different physiological needs. Practical diets with eight (0, 5, 10, 20, 40, 80, 160, 320 mg AA/kg diet) levels of ascorbic acid polyphosphate were fed to sea bass (mean weight: 0.7 g) for 15 wk. At the beginning and at the end of the feeding trial, tissues were sampled for vitamin C and hydroxyproline (HyPro) analysis. Dose-dependent responses of skin and whole body HyPro concentrations and hepatic AA concentration to dietary vitamin C levels were observed. Skin and whole body HyPro concentrations were low in sea bass fed AA-deficient diet, 217 and 15 nmol/g tissue, respectively. HyPro levels increased with increasing dietary levels, reaching plateaus of 297 and 45 nmol/g tissue in the skin and whole body at dietary vitamin C levels of at least 5 and 31 mg AA/kg. Hepatic AA level increased with increasing dietary levels, reaching a plateau of 474 pmol/g tissue in juveniles fed at least 121 mg of AA/kg. We concluded that hepatic AA saturation is the most stringent response criterion for determination of the vitamin C requirement in juvenile European sea bass.