Vitamin E increases natural cytotoxic activity in seabream (Sparus aurata L.)

The natural cytotoxic activity of head-kidney leucocytes from gilthead seabream (Sparus aurata L.), after in vitro and in vivo vitamin E treatment, against tumor cells was studied by flow cytometry. Leucocytes were incubated in culture medium with different vitamin E supplementations (0·01–10 μg ml−1) for 6, 24 or 48 h and the results demonstrate that all the assayed vitamin E supplementations significantly enhanced the natural cytotoxic activity of leucocytes. To determine the effect of a high dietary level of vitamin E on this activity, fish were fed with 0 (control), 600, 1200 or 1800 mg of vitamin E supplementation kg−1diet for 2, 4 or 6 weeks. After 2 and 4 weeks of treatment, the natural cytotoxic activity was significantly enhanced at the highest (1·8 g kg−1diet) and lowest (600 mg kg−1diet) vitamin E supplement dosage, respectively. No effect of the vitamin E supplemented diet on seabream leucocyte natural cytotoxic cell activity was observed after 6 weeks of treatment.