Natural cytotoxic activity in seabream (Sparus aurata L.) and its modulation by vitamin C

Isolated gilthead seabream head-kidney leucocytes were incubated in a culture medium supplemented with vitamin C (from 0—control—to 2 mg ml−1) or with a combination of different amounts of vitamin C (0·002 to 2 mg ml−1) and vitamin E (0·01 to 10 μg ml−1) for 6, 24 or 48 h. Afterwards, the cellular ascorbic acid content and the natural cytotoxic activity of leucocytes were evaluated. Leucocyte ascorbic acid levels were enhanced after incubation for 6–24 h with 0·2 mg of vitamin C ml−1 and above. The natural cytotoxic activity of leucocytes after incubation with vitamin C was also increased for all the assayed concentrations and incubation times except in the case of the highest vitamin C concentration (2 mg ml−1) and the longest incubation time (48 h). No statistically significant differences in leucocyte cytotoxic activity were observed when vitamin E was added to the vitamin C, compared with the results of vitamin C alone. e in vivo study, fish were fed diets supplemented with vitamin C (2·9 g kg−1 diet) without or with vitamin E (1·2 g of vitamin E kg−1 diet) for 2, 4 or 6 weeks. Serum lysozyme activity was enhanced to a statistically significant degree when fish were fed with the vitamin C+E supplemented diet for 2 weeks and with the vitamin C and vitamin C+E supplemented diets for 4 weeks. Both groups of fish showed a statistically significant increase in the natural cytotoxic activity of head-kidney leucocytes after 6 weeks of treatment although no differences were observed between treatments incorporating vitamin C alone or vitamin C combined with vitamin E.