S. Espelid et al., EFFECTS OF CORTISOL AND STRESS ON THE IMMUNE-SYSTEM IN ATLANTIC SALMON (SALMO-SALAR L), Fish & shellfish immunology, 6(2), 1996, pp. 95-110
A suppressive effect of cortisol on LPS mitogenesis was demonstrated o
n peripheral blood cells from Atlantic salmon (Salmo salar L.) in vitr
o, and the suppression was dose and time dependent. When cortisol was
injected intraperitoneally into fish, there was a rapid increase in th
e level of cortisol in the blood which was, however, effectively clear
ed from the circulation within a few hours. The number of cells in the
various populations of blood leucocytes was counted after cortisol ad
ministration demonstrating a marked increase in the relative number of
thrombocytes, while the number of granulocytes, monocytes and lymphoc
ytes was relatively constant. Qualitatively, however, the lymphocytes
seemed to be affected by cortisol, since the number of Ig positive cel
ls were dramatically downregulated during the first days after cortiso
l injection. A significant reduction in the mitogenic response of bloo
d lymphocytes to LPS was also observed and the response gradually retu
rned to normal levels over the next four days. When Atlantic salmon we
re ex:posed to repeated handling stress, there was no significant diff
erence in the total immunological status compared to non-stressed fish
as judged by antibody production and protection against Aeromonas sal
monicida infection. (C) 1996 Academic Press Limited