Production and Purification of Recombinant Somatolactin and its Effects on Insulin-like Growth Factors Gene Expression in Tilapia Hepatocytes

Somatolactin (SL), a member of the growth hormone (GH)/ prolactin (PRL) family, is fish-specific hormone as the gene has been lost in tetrapods during the period of land invasion [1]. It is well demonstrated that SL possesses both glycosylated and non-glycosylated forms in fish [2]. Biochemical and physiological studies demonstrated that SL might be involved in a variety of physiological actions including reproduction [3-5] smoltification [6] acid-base balance [7] background adaptation [8,9] phosphate transport [10] melanosome aggregation [11,12] and immune response [13]. Although major physiological actions of SL remain an interesting yet unresolved issue, direct evidences from mutant of medaka [14-16] and “cobalt” rainbow trout [17,18] support the concept that major functions of SL are involved in chromatophore regulation and lipid metabolism.