Modulation of fish phagocytic cells by n-terminal peptides of proopiomelanocortin (NPP)

N-terminal peptide of proopiomelanocortin (NPP, or pro-gamma -MSH) has show n to exhibit biological activity such as stimulation of adrenal mitogenesis and prolactin release-inhibiting factor activity. Structurally, studies re veal a significant difference between fish NPP from that of tetrapods, as N PPs from carp and salmonid lack gamma -MSH. Thus, fish NPP may exhibit func tions different from that of mammals. The activation of phagocytic cells by NPP was analysed using rainbow trout Oncorhynchus mykiss and carp Cyprinus carpio. Rainbow trout and carp macrophages incubated with chum salmon NPP significantly enhanced the production of superoxide anion in comparison wit h control macrophages (without hormones). Both rainbow trout and carp macro phages had shown increased phagocytosis when stimulated administered with N PP. The above results were complemented by in vivo studies where NPP was ad ministered to rainbow trout and carp. NPP significantly increased superoxid e anion production as well as phagocytosis in macrophages. These results sh ow that NPP in lower vertebrates activates the function of the phagocytic c ells. (C) 2001 Wiley-Liss, Inc.