Effects of intraperitoneal injection of cortisol on non‐specific immune functions of Ctenopharyngodon idella

Abstract

After grass carps Ctenopharyngodon idellus were injected with cortisol, with (CBC) and without (C) a cocoa butter carrier, the effects of both slowly and rapidly acting exogenous cortisol on their non-specific immune functions were investigated. On the one hand, after injection with CBC, the cortisol concentration and lysozyme activity in fish serum were enhanced and were sustained at high levels for a long period (30 days). The killing activity in the serum declined with time, and phagocytosis of head kidney macrophages diminished significantly (P < 0Á05 or P < 0Á01). The leukocrit values in the high dose group (31Á8 mg cortisol fish À1) increased over time, however, with the maximum average being 5Á6% at day 30. The spleen mass index in the high dose group was 0Á93 Â 10 À3 after 30 days, notably lower (P < 0Á05) than that in the control group. In addition, a decrease in resistance to Aeromonas hydrophila infection in cortisol-treated fish was shown, with the final cumulative mortalities being 54Á5 and 66Á7% in the low and high dose groups, respectively. On the other hand, there was a decrease in both serum cortisol concentration and lysozyme activity of the experimental fish within 2 weeks after injection with C, where plasma bactericidal activities in the high dose group (31Á8 mg cortisol fish À1 ) were remarkably lower (P < 0Á01) than those in the control group at each sampling, but were increased slightly over time. The results of which were different from those in the CBC trial. Phagocytic activity of head kidney macrophages and spleen mass index decreased significantly (P < 0Á05), while there were increases in leukocrit value and cumulative mortality due to A. hydrophila. The results of which were similar to those in the CBC trial. This study indicated that the injection of cortisol depressed the non-specific immune functions of the grass carp and increased its susceptibility to disease.

Effects on mortality and stress response in European sea bass, Dicentrarchus labrax (L.), fed mannan oligosaccharides (MOS) after Vibrio anguillarum exposure

“…Thus, at 4 h post‐stress/infection in fish fed the control diet, the higher mortality observed in infected (I), and stressed and infected (SI) fish could be associated with plasma cortisol levels higher than those seen in the MOS‐treated fish at the same time. While it is likely that higher infection levels contributed to this difference in cortisol levels between the dietary groups, it is also the case that fish with higher levels of cortisol have an increased susceptibility to disease (Pickering & Pottinger 1985; Harris, Soleng & Bakke 2000; Kenneth, Billy & Wayne 2003; Wang et al. 2005; Ellis et al.…”

Supraphysiological Cortisol Elevation Alters the Response of Wild Bluegill Sunfish to Subsequent Stressors

“…Nevertheless, these studies do not explicitly incorporate recovery time into an ecologically relevant context, where fish may be subjected to environmental stressors during or after the period of recovery from cortisol elevation. Also, almost all studies involving experimental cortisol elevation have been conducted in the laboratory and on domesticated fish (Vijayan et al, ’91; Morgan and Iwama, ; Gregory and Wood, ; Wang et al, ). Few studies have evaluated the long‐term consequences of chronic stress and multiple stressors in wild fish (see O'Connor et al, ), although there have been several relevant studies on wild birds.…”

In vivo treatment with progestogens causes immunosuppression of carp Cyprinus carpio leucocytes by affecting nitric oxide production and arginase activity

“…Injection with steroids in a cocoa butter carrier (CBC) has been successfully applied as a method of slow release of hormones (Carlson et al , 1993; Wang et al , 2005) and was adopted in the present experiment to administer steroid compounds to the fish. The steroid compounds were dissolved in ethanol (final concentration of 0·01%) and added to melted cocoa butter (37° C, Thermo‐Shaker TS‐100, Lab4You GmbH; http://www.lab4you.de) to a final concentration of 1 mg steroid compound kg −1 fish.…”