Involvement of Polyamine in Growth Hormine Secretion from the GH3 Cells / 대한내분비학회지

ABSTRACT

BACKGROUNDS Polyamines are known to be essential for cell growth and differentiation. Recently, possible roles of the polyamine in signal transduction as neurotransmitter, modulator, or second messenger are suggested in many studies. Furthermore, it is widely studied that possible roles of polyamine are involved in the action of hormone. Thus, it was to investigate the effect of polyamines in the cell proliferation and secretion of GH from the GH cells. METHODS: Cells(5*10 cells/mL) were incubated for 3 days in DMEM containing test drugs and labeled with 20pCi/mL of [S]-methionine for 2 hr. Proteins secreted into the medium were separated by 13% SDS-gel electrophoresis, then autoradiography was performed to identify radiolabeled proteins. [S]-methionine labelled GH was identified by radioimmuno-precipitation. Total protein synthesis was determined from the radioactivity of the cell homogenate by liquid scintillation counter. The intracellular polyamine content was determined by HPLC. RESULTS: Externally added polyamines(putrescine, spermidine, spermine) induced cell proliferation in a dose-dependent manner at proper concentrations, specifically 50pM putrescine increased GH secretion, DFMO or MGBG, which is polyamine biosynthetic inhibitor, inhibited GH secretion in a dose-dependent fashion, In the cells treated with 20mM or 0.01mM MGBG, total protein synthesis were decreased only to 90 or 76% of the control levels and cell proliferation was also slightly inhibited. However the secretion of GH was severely blocked to 37% or 35% of the control. Hydrocortisone at 5 pM stimulated the secretion of GH to 153% of basal secretion, also doubled intracellular putrescine content. CONCLUSION: The present data show that externally added polyamines induced cell proliferation and GH secretion. Also, extemally added putrescine stimulated GH secretion significantly. GH secretion was inhibited by polyamine metabolic inhibitor in a dose-dependent manner and polyamine metabolic inhibitors, at proper concentrations, specifically blocked GH secretion without any significant influence on the total protein synthesis. The above results imply the involvement of polyamine in GH secretion.