Kidney leucocytes of rainbow trout, Oncorhynchus mykiss, are activated by intraperitoneal injection of β-endorphin

The immunomodulatory effects of β-endorphin were studied by measurements of the production of superoxide anion, phagocytosis and chemotaxis of kidney phagocytic cells in rainbow trout, Oncorhynchus mykiss. The production of superoxide anion in phagocytic cells increased significantly in rainbow trout injected with chum salmon β-endorphin. The responses were dose-dependent. The phagocytosis and chemotaxis also significantly increased in kidney phagocytic cells of rainbow trout injected with β-endorphin. These results show that β-endorphin in rainbow trout activates the function of phagocytic cells in vivo.