Involvement of JNK activity in GnRH I and II-induced MMP-26 production. A, B6Tert-1 cells were stimulated with GnRH I or GnRH II (100 nM) for 5, 10 and 30 min, or the cells were left untreated as a control. Phosphorylation of ERK1/2 or JNK and the total amount of ERK1/2 or JNK were determined by Western blotting analyses. B. Following 30-minute pretreatment with PD98059 (10 μM, ERK1/2 inhibitor) or SP600125 (10 μM, JNK inhibitor), B6Tert-1 cells were treated with GnRH I or GnRH II (100 nM) for 24 h and the protein levels of MMP-26 analyzed by Western blotting analyses. Levels of protein for MMP-26 were normalized to the corresponding β-actin. The results derived from both these analyses as well as those from at least three other sets of experiments were standardized to the untreated control and are represented (mean ± SEM; n ≥ 3) in the bar graphs (*, P < 0.05 vs. bar a; #, P < 0.05 vs. bar b; &, P < 0.05 vs. bar c).