Histone-like proteins from Atlantic cod milt: stimulatory effect on Atlantic salmon leucocytes in vivo and in vitro

This study was carried out to reveal some characteristics of cationic proteins from Atlantic cod (Gadus morhua) milt chromatin and to investigate their ability to activate Atlantic salmon (Salmo salar) macrophages. Cationic proteins extracted from cod milt chromatin were fractionated on a cation exchange chromatography column. SDS-PAGE and amino acid analyses of the resulting fractions indicated that these proteins are similar to calf thymus histones. Two cationic protein fractions were used to stimulate leucocytes from Atlantic salmon in vitro and in vivo. Increased production of superoxide, measured as reduction of nitroblue tetrazolium (NBT), was used as indication of macrophage activation. Both fractions induced elevated superoxide anion production in the macrophages after 3 and 6 days of in vitro stimulation. Intraperitoneal injection of the cationic protein fractions in Atlantic salmon (100 mg kg(-1)) four days prior to slaughtering stimulated superoxide production when assayed after one and two days of cell cultivation. In macrophages from fish slaughtered two days after injection, activation could first be seen after two days of cell cultivation.