Effect of GnRH-I and GnRH-II on the cell growth. HEC1A cells were treated with GnRH-I or GnRH-II analog (10 nM or 100 nM) for 24 h in serum-free medium. Cell proliferation was determined by 3H-thymidin incorporation assay following treatment with GnRHs. Values are the means of cell number (± S.E.) in triplicates of three independent experiments. a, indicates p < 0.05 vs. control (cont).