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

INTRODUCTION
increase their bactericidal activity, oxygen dependent and independent mechanisms
being involved (Siwicki et al., 1994; Anderson, 1996).
Immunostimulants may be able to compensate some chemotherapeutic and vaccine
limitations. Immunostimulants are safer than chemotherapeutics and their range of
efficacy is wider than vaccination. However, we cannot expect the marked or long-term
effects observed with vaccines to occur with immunostimulants because these
substances act on non-specific immune system, without a memory component
(Anderson, 1996; Sakai, 1999). Sakai (1999) suggests that the most effective strategy to
prevent and combate possible infectious diseases in fish, is the combination of
immuostimulants and vaccines. Thus, with a detailed understanding of the efficacy and
limitations of immunostimulants, they may become powerful tools to control fish
diseases.
4.3. USE OF ALGAE AS IMMUNOSTIMULANTS
During last years searching for therapeutically active substances has focused on
marine organisms. Ability of algae to produce secondary metabolites, such as
antibiotics, antivirals, antitumorals and antiinflammatories, with potential
pharmaceutical interest, has been well documented (Scheuer, 1990; Faulkner, 1993;
González del Val et al., 2001). However, studies on immunomodulatory properties of
extracts and whole cells from algae are still scarce. In this Thesis we have studied the
red microalga Porphyridium cruentum as a possible source of immunostimulants in
cultured sole.
A great number of algae constitute an important source of polyunsaturated fatty
acids (PUFAs), which are the essential dietary requirements for many marine teleosts
(Bell et al., 1985; Koven et al., 2001). Some of these fatty acids, such as the arachidonic
acid, AA (20:4(n-6)) participate in eicosanoid synthesis, therefore, in prostaglandin
production, involved in stress through modulation of cortisol release and, therefore in
cellular immunity (Villalta et al., 2005).
Algae also contain carotenoids, β-carotene, astaxanthin, cataxanthin or
xanthofilins. Amar et al. (2004) demonstrated that β-carotene, isolated from Dunaliella
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