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چکیده
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The objective of this study was to assess the ability of natural carotenoid oxidation products derived from beta-carotene (OxC-beta, Chemaphor Inc.) to modulate respiratory burst (RB) and bactericidal activity (BA) in primary rainbow trout leukocyte cultures (PRTLC). In vitro experiments involved measuring the RB of naïve primary leukocytes and primary leukocytes previously primed in vitro (24 hrs) with various concentrations (0, 10, 20, 40 ppm) of OxC-beta and then stimulated with PMA (1 ug/ml), Aeromonas salmonicida LPS (ASAL LPS, 10ng/ml), 1% DMSO or various concentrations OxC-beta dissolved in 1% DMSO vehicle control for 1 hr. OxC-beta exposure significantly increased the RB of both non-primed and primed PRTLC and there was an overall higher RB in leukocytes initially primed (24 hr) with 1.0μM OxC-beta regardless of stimulant used. OxC-beta treatment produced significantly increased BA in PRTLC when compared to leukocytes with no OxC-beta treatment or DMSO controls. An in vivo feed trial using commercial trout feed incorporating various concentrations (0, 10, 20, 40 ppm) of OxC-beta was also performed; for each treatment, three groups of 50 fish were fed 1.5- 2% body weight per day and PRTLC were isolated from 8 fish per group on days 1, 6, 10 and 16 and used in in vitro assays as described above. There was a significant increase in RB of PRTLC between groups of fish fed 20ppm OxC-beta compared with other concentrations, and the most dramatic effect was seen on Day 1. Similarly, there was a significant increase in BA on Day 1 of RTPLC from groups of fish fed any concentration of OxC-beta.
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