The effect of cortisol administration on blood plasma immunoglobulin M (IgM) concentrations in masu salmon (Oncorhynchus masou)

Abstract

Immunoglobulin M (IgM) is known as a main factor in the humoral immune system of teleosts. In the present study, the effect of cortisol on plasma IgM concentrations was investigated using a specific antibody to IgM in masu salmon (Oncorhynchus masou). Cortisol was orally administered each day for 2 weeks at a dose of 1 mg g(-1) in the diet, and for the following week the fish were fed a non-treated diet. Blood plasma samples were collected at 0, 1, 2 and 3 weeks after the initiation of treatment. Oral administration of cortisol elevated plasma cortisol concentrations to about 40 ng/ml for 2 weeks after administration and slightly reduced plasma IgM concentration; the suppression was statistically significant one week after the period of hormone administration. However, treatment with cortisol did not affect plasma concentrations of total protein or α1-protein, one of the major serum proteins, during the experimental period. These results indicate that cortisol specifically suppresses plasma IgM concentrations.

Inhibitory Effect of Cortisol on the Defense Activities of Tilapia Neutrophils in Vitro.

“…In channel catfish Ictalurus punctatus, Ellsaesser and Clem (1987) showed cortisol treatment in vivo led to lymphopenia and neutrophilia. Nagae et al (1994) demonstrated that cortisol suppressed plasma immunogloblin M in masu salmon Oncorhynchus masou.…”

Serum haemolytic and agglutinating activity as indicators of fish immunocompetence: their suitability in stress and dietary studies

“…Injection of cortisol in coho salmon, Oncorhynchus kisutch, has been shown to produce changes in leukocyte numbers (Maule et al,1987), but no changes in lymphocyte numbers in brown trout, Salmo trutta (Pickering and Pottinger, 1985). Cortisol causes reduction in the percentage of phagocytosis and the B lymphocytes in channel catfish, Ictalurus punctatus (Ainsworth et a/.,1991), and reduction of IgM levels in masu salmon, O. masou (Nagae et al, 1994). In addition, it has been shown in mammals that glucocorticoids reduce the formation of basic interface molecules such as interleukins (Khansari et al, 1990;Amano et al, 1993) and similar processes have been shown in fish (Kaatari and Tripp, 1987;Schreck, 1990, 1991).…”

Changes in Transcript Levels of Gill Cortisol Receptor during Smoltification in Wild Masu Salmon, Oncorhynchus masou

“…Cortisol concentration was measured according to the radioimmunoassay method reported by Nagae et al (1994).…”