Effect of high dietary intake of vitamin C on non-specific immune response of gilthead seabream (Sparus aurata L.)

Abstract

To determine the effect of a high level of dietary intake of ascorbic acid (vitamin C) on the non-specific immune response of gilthead seabream (Sparus aurata L.), specimens were fed diets containing 500mg kg−1(control) and 3,000mg kg−1ascorbic acid for 2, 4, 6, 8 or 10 weeks. Growth, serum level of vitamin C, natural haemolytic complement activity and head-kidney leucocyte migratory, respiratory burst and phagocytic activities were studied at each one of the assayed times. A positive relationship between vitamin C intake and serum ascorbic acid was observed, the enhancement being evident after 2 weeks of administration and maintained until 10 weeks. Specimens fed a vitamin C supplemented diet showed a slightly higher (but no statistically significant) specific growth rate than fish fed the control diet. The non-specific immune response parameters assayed were enhanced by the dietary intake of vitamin C although, each one peaked at a different time: phagocytic activity after 2 weeks of administration, natural haemolytic complement activity after 6 weeks, respiratory burst after 8 weeks. However, leucocyte migration was not affected. The results indicated that the serum ascorbate concentration of specimens fed a high level of vitamin C reach a plateau. The non-specific immune response parameters assayed increased as a consequence of a high vitamin C supply, although the increase was not maintained but returned to the initial levels. This suggests that the immune response accomodates to the new high vitamin C plasma availability after a transient enhancement.