Involvement of Growth Hormone and Prolactin in the Induction of Vitellogenin Synthesis in Primary Hepatocyte Culture in the Eel, Anguilla japonica

Multihormonal effects of bovine growth hormone (GH) and ovine prolactin (PRL) on vitellogenin (Vg) synthesis in response to estradiol-17 beta (E2) were electrophoretically examined in primary hepatocyte culture in the eel, Anguilla japonica. Newly synthesized protein after hormonal treatment was identified as Vg by immunoblot and immunoelectrophoresis. A single injection of E2 into hypophysectomized eels failed in the induction of Vg synthesis. Similarly, E2 alone was insufficient to induce Vg synthesis in the culture. On the other hand, the combination of E2 with GH and/or PRL markedly stimulated Vg synthesis. Neither GH alone nor PRL alone had any effect on the induction of Vg synthesis by cultured hepatocytes. Hepatocytes isolated from E2-primed eels also required GH or PRL for continuation of Vg synthesis. The highest Vg synthesis occurred at doses of 50 ng GH/ml and 1 microgram PRL/ml in the presence of 2 x 10(-6) M E2. These results indicate that the multihormonal stimulation of GH and/or PRL as well as E2 is essential for the active synthesis of Vg in eels.