Papel de las actividades superóxido dismutasa y catalasa en la ...

are in agreement with the data reported by Castro et al. [35], who observed increases in
the respiratory burst activity of the head kidney phagocytes of turbot and gilthead
seabream incubated with different concentrations of β-glucans obtained from fungi and
yeasts. The fact that several authors found significant variations in the stimulatory
capacities of algal extracts depending not only on their origin, but on the concentrations
used and time of incubation [23] does not rule out a potential in vitro modulation of
respiratory burst activity by P. cruentum extracts. Thus, higher concentrations and
longer incubation times need to be assayed.
The results obtained in the in vivo assays showed that fish immunized with a
bacterin against P. damselae subsp. piscicida and receiving the diet supplemented with
the alga P. cruentum significantly increased the respiratory burst activity of their
phagocytes after four weeks of the feeding treatment. This increase was higher than that
obtained in the group of fish fed with the diet supplemented with Sanostim for four
weeks. These stimulated phagocytes may be more efficient in the inactivation of
intracellular pathogens such as P. damselae subsp. piscicida than other phagocytes
which had not been in contact with the components of the alga assayed. However,
experiments to test the bactericidal activity of phagocytes from sole specimens fed with
this diet should be considered in order to confirm this hypothesis.
Evidence is increasing to support the essentiality of nutrients for maintaining a
normal immune system in fish [22, 36]. These nutrients are proteins, essential fatty
acids, polysaccharides, vitamins C and E, and some oligoelements such as Se and Zn
[37, 38]. P. cruentum is a red microalga member of Rodophyta, of the order of
Porphyridiales, with spherical cells that lack a rigid cell wall. This alga accumulates
large amounts of lipids, specially arachidonic acid and noticeable amounts of
eicosapentaenoic acid, these being substances which have been reported as
immunostimulants [39, 40]. The available carbohydrates ranged from 40 to 57% [41].
Different carbohydrates have been reported previously as immunostimulant active on
fish phagocytes [7, 23, 33, 40-48]. Morris et al. [26] suggested a potential
immunostimulant activity of the polysaccharides isolated from cultures of P. cruentum
on the metabolic and functional action of mice phagocytes. This alga also contains large
amounts of carotenes [41] and several studies have reported that the carotenoids
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