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

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 (Sparu s aurata L.), specimens were fed diets containing 500 mg kg(-1) (control) a nd 3,000 mg kg(-1) ascorbic 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 studi ed at each one of the assayed times. A positive relationship between vitami n C intake and serum ascorbic acid was observed, the enhancement being evid ent after 2 weeks of administration and maintained until 10 weeks. Specimen s fed a vitamin C supplemented diet showed a slightly higher (but no statis tically significant) specific growth rate than fish fed the control diet. T he non-specific immune response parameters assayed were enhanced by the die tary intake of vitamin C although, each one peaked at a different time: pha gocytic activity after 2 weeks of administration, natural haemolytic comple ment activity after 6 weeks, respiratory burst after 8 weeks. However,:Leuc ocyte migration was not affected. The results indicated that the serum asco rbate concentration of specimens fed a high level of vitamin C reach a plat eau. The non-specific immune response parameters assayed increased as a con sequence of a high vitamin C supply, although the increase was not maintain ed but returned to the initial levels. This suggests that the immune respon se accomodates to the new high vitamin C plasma availability after a transi ent enhancement. (C) 1999 Academic Press.