Arachidonic acid reduces the stress response of gilthead seabream Sparus aurata L.

Abstract

In this study the influence of the dietary level of the fatty acid arachidonic acid (ArA, 20:4n-6) was determined on the acute stress response and osmoregulation of adult gilthead seabream Sparus aurata L. Seabream were fed a diet containing either 0.9% or 2.4% of total fatty acids as ArA for 18 days before being subjected to a 5·min period of net confinement. Prior to this stressor, a subgroup of fish from both dietary treatment groups was treated with acetylsalicylic acid (ASA), an irreversible blocker of cyclooxygenase (COX). This would indicate whether any effects were caused by an enhanced synthesis of prostaglandins derived from ArA. The highest ArA levels were found in the kidneys, and these were further enhanced by dietary ArA-supplementation. In gill tissues, there were significant changes in all selected fatty acid classes 24 h after confinement, except for the docosahexaenoic acid (DHA, 22:6n-3) : eicosapentaenoic acid (EPA, 20:5n-3) ratio. ArA feeding strongly reduced the cortisol response to confinement, which was partially counteracted by ASA treatment. ArA also attenuated the stress-associated increase in plasma osmolality and, in combination with ASA, enhanced the osmolality and plasma chloride levels, but reduced plasma sodium levels after confinement. Furthermore, ArA enhanced the branchial Na + , K + -ATPase activity both before and after confinement, whereas feeding ASA diminished this effect. It appeared that the effects of ArA-supplementation could not always be ascribed to an increase in prostaglandin synthesis. It is advisable to determine the long-term effects of replacing fish oils in commercial diets with vegetable oils that contain no long-chain fatty acids, particularly in carnivorous/marine species with low fatty acid elongation and desaturation activities. The effects of a low dietary intake of ArA (and other polyunsaturated fatty acids) should be studied over a longer term, taking into account any consequences for the health of the fish.

Dietary metal and macro-nutrient intakes of juvenile lemon sharks determined from the nutritional composition of prey items

“…However, the whole body Na concentration in this study (8-16 mg g -1 , Table 2) were, as expected, slightly higher than that of rainbow trout in freshwater (e.g. 0.7-1 mg g , Van Anholt et al 2004). Whole body K appears to be rarely reported in fish, but the concentrations here (7-12 mg g -1 , Table 2) were similar to freshwater trout (~6 mg g based on 1.34 ± 0.1% of body weight per day for a 1.85 kg lemon shark (n = 397; Newman et al 2010).…”

“…For the fish species in Table 2 there appear to be no previous reports detailing the major electrolyte composition of the whole carcass. However, the whole body Na concentration in this study (8-16 mg g , Van Anholt et al 2004). Whole body K appears to be rarely reported in fish, but the concentrations here (7-12 mg g Table 2).…”

Criteria for Safe Use of Plant Ingredients in Diets for Aquacultured Fish

“…In an interesting set of studies, Van Anholt and colleagues tested the effect of 20:4n-6 and acetylsalicylic acid in gilthead sea bream. When adult fish were fed diets supplemented with 20:4n-6, the stress response was reduced when subjected to confinement stress, and partially counteracted by acetylsalicylic acid (Van Anholt et al 2004b). When similar studies were carried out in larval sea bream, 20:4n-6 again reduced the cortisol response and increased survival of fish subjected to air exposure stress.…”

The effects of arachidonic acid on the endocrine and osmoregulatory response of tilapia (Oreochromis mossambicus) acclimated to seawater and subjected to confinement stress

“…On the other hand, ArA can function as a second messenger itself and can directly stimulate steroidogenesis by altering the activity of protein kinase A and protein kinase C, enzymes that control the production of cortisol (Axelrod et al 1988;Kallen et al 1998;Lacroix and Hontela 2001;Naor 1991). In contrast, the same dietary ArA supplementation reduced plasma cortisol levels before as well as after confinement in (SW) gilthead sea bream (Sparus aurata;Van Anholt et al, 2004b). The mechanism underlying the contrasting effects of ArA supplementation in SW compared with FW tilapia, and in tilapia compared with gilthead sea bream, needs to be elucidated, but it could be analogous to the stimulating of the release of prostaglandins in gill homogenates of rainbow trout by external salinity (Brown et al 1991;Beckman and Mustafa 1992).…”