Relationship between vitamin C and plasma concentrations of testosterone in female rainbow trout, Oncorhynchus mykiss.

Two-year old rainbow trout females were fed diets containing 0, 30, 110, 220, 440 and 870 mg kg(-1) ascorbyl-2-monophosphate Mg(+) salt (groups 1, 2, 3, 4, 5, and 6, respectively) from August until March. At the time of spawning (February-March) blood was sampled and the ovulating females were hand stripped. Estradiol (E2) and testosterone (T) concentrations in plasma, and ascorbic acid (AA) concentrations in plasma and eggs were determined. The mean plasma concentrations of T were higher in group 4, 5, or 6 than in group 2 or 3 (p < 0.05). Moreover, the average plasma concentration of T in fish fed the diets with AA level below National Research Council (NRC) recommendations (groups 1, 2 and 3) was significantly lower (p<0.01) than the average plasma concentration in fish fed diets with AA level above NRC recommendations (groups 4, 5, and 6). These data are consistent with the hypothesis that AA can influence production of steroids in female rainbow trout.